• Resection rate [ Time Frame: Through the study peirod, for 3 years ]
  The proportion of patients with surgeical treatment after treatment
• R0 rate [ Time Frame: Through the study peirod, for 3 years ]
  The proportion of patients with completely tumor resection after treatment
• Objective response rate [ Time Frame: Through the study peirod, for 3 years ]
  The proportion of patients with tumor size reduction of a predefined amount and for a minimum time period
• Disease control rate [ Time Frame: Through the study peirod, for 3 years ]
  The proportion of patients with tumor size reduction or stable
• Overall survival [ Time Frame: Through the study peirod, for 3 years ]
  The time of treatment until death.
• EORTC QLQ - PAN26 score [ Time Frame: Through the study peirod, for 3 years ]
  QLQ score assessed by the European Organization for Research and Treatment of Cancer Quality of Life scale for pancreatic cancer
• Adverse effects [ Time Frame: Through the study peirod, for 3 years ]
  The most common hematologic and non-hemotologic adverse events
• Carbohydrate antigen 19-9 [ Time Frame: Through the study peirod, for 3 years ]
  Carbohydrate antigen 19-9 level

• Resection rate [ Time Frame: Through the study peirod, for 2 years ]
  The proportion of patients with surgeical treatment after treatment
• R0 rate [ Time Frame: Through the study peirod, for 2 years ]
  The proportion of patients with completely tumor resection after treatment
• Objective response rate [ Time Frame: Through the study peirod, for 2 years ]
  The proportion of patients with tumor size reduction of a predefined amount and for a minimum time period
• Disease control rate [ Time Frame: Through the study peirod, for 2 years ]
  The proportion of patients with tumor size reduction or stable
• Overall survival [ Time Frame: Through the study peirod, for 2 years ]
  The time of treatment until death.
• EORTC QLQ - PAN26 score [ Time Frame: Through the study peirod, for 2 years ]
  QLQ score assessed by the European Organization for Research and Treatment of Cancer Quality of Life scale for pancreatic cancer
• Adverse effects [ Time Frame: Through the study peirod, for 2 years ]
  The most common hematologic and non-hemotologic adverse events
• Carbohydrate antigen 19-9 [ Time Frame: Through the study peirod, for 2 years ]
  Carbohydrate antigen 19-9 level

• No Intervention: Chemotherapy group
  Treatment with modified-FOLFIRINOX Folic acid 400mg/m^2, 5- fluorouracil 2400mg/m^2 for 46h, irinotecan 135mg/m^2 and oxaliplatin 68mg/m^2
• Experimental: Combination group
  Treatment with modified-FOLFIRINOX and Anti-PD-1 antibody Folic acid 400mg/m^2, 5- fluorouracil 2400mg/m^2 for 46h, irinotecan 135mg/m^2 and oxaliplatin 68mg/m^2, Anti-PD-1 antibody 3mg/kg
  Intervention: Drug: Anti-PD-1 monoclonal antibody

Inclusion Criteria:

• Pathologically (histologically or cytologically) confirmed pancreatic ductal adenocarcinoma (PDAC).
• No evidence of distant metastasis (such as liver, peritoneum, lung) evaluated by abdominal contrast-enhanced CT, MRI, and chest CT. PET/CT or other imaging examinations would be used if necessary.
• Initial assessment for definitive borderline resectable or locally advanced tumors (resectability judgment is based on CT enhanced scan or magnetic resonance imaging, NCCN2019 first edition standard).
• ECOG score 0 or 1.
• Serum creatinine level is normal, and serum total bilirubin level is less than 1.5 x ULN.
• ALT and AST are less than 2 x ULN.
• If biliary obstruction is observed, biliary decompression should be performed when the patient is randomly assigned to receive neoadjuvant chemotherapy.
• Leukocyte count (> 3.5 x 10^6 /mL), neutrophil count (> 1.5 x 10^6 /mL), platelet count (> 80 x 10^6 /mL), hemoglobin (> 9 g/dL).
• Signed informed consent.

Exclusion Criteria:

• History of malignance treatment in the past, excluding basal and cutaneous squamous cell carcinoma, cervical carcinoma in situ, papillary thyroid carcinoma
• History of participation of other clinical trails within 4 weeks
• History of immunotherapy within 4 weeks
• History of receiving chemotherapy, radiotherapy and molecular target therapy within 2 weeks
• Tumor is a local recurrent lesion.
• Imaging confirmed severe portal hypertension / cavernous transformation.
• Ascites
• Gastric outlet obstruction
• Respiratory failure requires supplementation of oxygen.
• Immune deficiency syndrome, such as active tuberculosis and HIV infection.
• Hematological precancerous diseases, such as myelodysplastic syndromes.
• Major cardiovascular diseases (including myocardial infarction, unstable angina, congestive heart failure, severe uncontrolled arrhythmia) during the past six months of enrollment.
• Evidence of clinical-related or previous interstitial lung disease, such as noninfectious pneumonia or pulmonary fibrosis, or baseline chest CT scan or chest X-ray findings
• Previous or physical findings of central nervous system disease, except for adequately treated (e.g. primary brain tumors, uncontrolled seizures or strokes with standard medications)
• Preexisting neuropathy > 1 (NCI CTCAE).
• Allograft requires immunosuppressive therapy or other major immunosuppressive therapies.
• Severe serious wounds, ulcers or fractures.
• Confirmed coagulant disease.
• Clinical evaluation is unacceptable.