A Prospective, Randomized, Double-blinded, Multi-center Clinical Trial to Evaluate the Efficiency and Safety of Anti-PD1 Antibody (Camrelizumab) Combined With Paclitaxel(Albumin Bound) and Gemcitabine as First-line Therapy in Patients With Metastatic Pancreatic Cancer

Inclusion Criteria:

* 1\. Aged \>= 18 years, male or female; 2. Histologically or Cytologically confirmed metastatic pancreatic adenocarcinoma; 3. Patients have never received systematical anti-cancer therapy; 4. Based on Response Evaluation Criteria In Solid Tumors (RECIST1.1), there should be at least one measurable lesion which has never received local treatment like radiotherapy(The lesion located in previous radiotherapy areas can also be selected as target lesions if the progress confirmed.) 5. ECOG:0-1; 6. Expected survival\>=12 weeks; 7. Essential organs function must meet the following criteria (Any blood products, growth factor, leucocyte promoting drugs, platelet promoting drugs, drugs for anemia are not allowed in 14 days before the first use of the experimental medication):

  1. Absolute neutrophil count(ANC) \>= 1.5x10\^9/L
  2. Platelet \>= 85x10\^9/L
  3. Hemoglobin \>= 90g/L
  4. Serum Albumin \>= 30g/L
  5. Total bilirubin \<= 2.0 ULN (Biliary obstructive patients after biliary drainage \<= 2.5 ULN), AST and ALT \<= 3.0 ULN (patients with liver metastasis \<= 5 ULN);
  6. Creatinine clearance rate \>60 mL/min;
  7. Activated Partial Thromboplastin Time and International Standardized Ratio \<= 1.5 ULN (Patients using stable dose of anticoagulant therapy such as low molecular weight heparin or warfarin and INR is within the expected range of anticoagulants can be selected.)

Exclusion Criteria:

* 1\. Patients with central nervous system metastasis. 2. Patients only have local advanced diseases. 3. Patients have uncontrolled pleural, pericardial or abdominal effusion requiring drainage.

  4\. Patients with history of allergy to monoclonal antibodies, any component of SHR-1210, paclitaxel(Albumin Bound) and Gemcitabine.

  5\. Patients have ever received anti PD-1 or anti PD-L1 therapy in the past. 6. Patients have accepted any experimental medication.within 4 weeks before the first dose of our experimental medication administration.

  7\. Patients are enrolled in another clinical trial except for observational clinical trial (Non-interventional) or the follow-up of the interventional clinical trial. 8. Patients accepted the last dose of anti-cancer therapy (including radiotherapy) within 4 weeks before the first dose of experimental medication administration.

  9\. Patients who need corticosteroid or other immunosuppressive agents. 10. Patients who ever received anti-cancer vaccine or have received live vaccine within 4 weeks before the first dose of administration.

  11\. Patients who have received major surgery within 4 weeks before the first dose of administration.

  12\. Patients with active autoimmune diseases, history of autoimmune diseases. 13. History of immunodeficiency, including HIV positive test, or other acquired, congenital immunodeficiency disorders, or history of organ transplantation and allogeneic bone marrow transplantation.

  14\. Patients with uncontrolled cardiovascular clinical symptoms or diseases. 15. Severe infections occurred within 4 weeks before the first administration. 16. History of interstitial lung disease and non- infectious pneumonia. 17. Patients with active pulmonary tuberculosis (APTB) infection confirmed by medical history or CT examination.

  18\. Patients with active hepatitis B or hepatitis C. 19. Patients with any other malignant tumors diagnosed within 5 years before the first administration.

  20\. Pregnant or lactating women. 21. According to the researchers, participants have other factors that may force them to end up the study.