Inclusion Criteria:
* Nasopharyngeal carcinoma diagnosed by pathology or cytology.
* Primarily metastatic (stage IVB as defined by the International Union against Cancer and American Joint Committee on Cancer staging system for NPC, eighth edition) is not amenable for local-regional treatment or curative treatment.
* Has not received prior systemic treatment for metastatic nasopharyngeal carcinoma, except for neoadjuvant chemotherapy, concurrent chemoradiotherapy, or adjuvant chemotherapy 6 months prior to the first treatment.
* The Karnofsky performance status score is at least 70 points (if the decreased score is caused by the tumor, the minimum score can be 50 points after the judgment of researchers.)
* Has at least one measurable target lesion based on RECIST v1.1, which is never received local treatment like radiotherapy.
* Life expectancy ≥ 3 months.
* The lab examination results of the screening must fulfill all of the following (use of any blood components, hematopoietic stimulating factors, etc. are not allowed within 14 days before screening):
1. absolute neutrophil count ≥1.5×10\^9/ L;
2. platelet count ≥ 100×10\^9/ L;
3. hemoglobin ≥ 8.0 g/dL;
4. serum albumin ≥ 2.8g/dL;
5. aspartate transferase(AST) and alanine transferase(ALT) ≤ 1.5 ×ULN; total bilirubin ≤ 1.5×ULN (if has liver metastasis, AST and ALT ≤ 5×ULN);
6. creatinine clearance \>50 mL/min.
* Men with reproductive capacity or women of childbearing potential must use highly effective contraceptive methods during the trial (e.g., oral contraceptives, intrauterine device, sexual abstinence or barrier method combined with spermicide), and continue contraception for 3 months after the last injection of JS001 and 6 months after the end of chemotherapy.
* Has signed the Informed Consent Form.
Exclusion Criteria:
* Allergic to monoclonal antibodies, any JS001 components, gemcitabine, cisplatin, or 5-fluorouracil.
* Has prior therapy including anti-PD-1, anti-PD-L1, or CTLA4.
* Major surgery within 28 days prior to the randomization (not including diagnostic surgery) or plan to be conducted during the study.
* Active autoimmune disease requiring systemic treatment or has a history of autoimmune disease.
* Requiring the use of cortisol (\>10mg/day Prednisone or equivalent dose) or other systematic immunosuppressive medications within 14 days before the study treatment.
* Allergic to macromolecular protein preparation ingredients.
* Has central nervous system (CNS) metastasis with clinical symptoms.
* Had other invasive malignant diseases, except excised basal-cell skin carcinoma, cervical carcinoma in situ, or other cancers curatively treated more than 5 years before study entry.
* Has cardiac clinical symptoms or disease out of control.
* Has an active infection or unexplained fever with more than 38.5 ℃ during screening and prior to first administration.
* Has acquired or congenital immune-deficient disease, or active hepatitis.
* History of drug abuse or alcohol abuse.
* The investigator judges other factors that may lead to the forced termination of this study, including but not limited to: other serious conditions (including mental disorder) that require concomitant treatment, severe laboratory test abnormalities, family or social factors that may affect the safety of patients or the collection of trial data and samples.
* Pregnancy or breast feeding.
