Background: The combination regimen of gemcitabine plus S1 (GS) as first-line chemotherapy has shown good efficacy in advanced pancreatic cancer. However, it is inconvenient to deliver gemcitabine on days 1 and 8 within one treatment cycle. In addition, previous studies have demonstrated that the gemcitabine administration by fixed dose rate infusion of 10 mg/m²/min should maximize the rate of intracellular accumulation of gemcitabine triphosphate and might improve clinical efficacy. The aim of this study was to evaluate the efficacy and safety of biweekly gemcitabine at fixed dose rate infusion combined with S1 (FGS) in chemonaive patients with locally advanced or metastatic pancreatic cancer. Methods: Forty-three eligible patients with locally advanced or metastatic pancreatic cancer received gemcitabine at a fixed dose of 10 mg/m²/min intravenously over a 2-h period on day 1, together with oral S1 40mg/m²twice daily on days 1 to 10, every 2 weeks. Tumor assessment was performed for every 3 cycles of chemotherapy. Results: All patients were evaluable for toxicity and 42 patients for efficacy. The overall response rate was 35.7% with 1 complete response, 14 partial responses, 17 stable diseases, and 10 progressions. Median time to progression was 5.9 months and median overall survival was 9.6 months. The main grade 3/4 toxicities included neutropenia (30.2%), thrombocytopenia (6.9%), anemia (2.3%), nausea (4.6%), diarrhea (2.3%). Conclusions: The biweekly FGS regimen is active, well tolerated and conveniently delivered as first-line chemotherapy for patients with locally advanced or metastatic pancreatic cancer.