Abstract: OBJECTIVE To observe the efficacy and safety in patients with advanced pancreatic cancer sequential chemotherapy with single-agent S-1 following gemcitabine plus S-1 initial first-line therapy. METHODS Thirty-two patients of advanced pancreatic cancer who received first-line chemotherapy with gemcitabine plus S-1 for 4 cycles, after achieving disease stabilization were randomized(1∶1 fashion) to receive single-agent S-1 sequential chemotherapy (80 mg·m·d^-1) for 14 days(S-1 group) or observation without treatment (observation group) until progression of disease, 21 days for a period of treatment. The outcomes of eligible randomized controlled trials included progression-free survival(PFS), overall survival(OS) and toxicities. RESULTS Thirty-two patients were evaluable for toxicity and survival in two groups. Median PFS and OS of S-1 group versus observation group were 7.0 months(95%CI, 6.6-7.4) vs 5.2 months(95%CI, 4.6-5.8) (P<0.05), and 10.7 months(95%CI, 9.9-11.5) vs 7.5 months(95%CI, 6.3-8.7) (P<0.05), respectively. The median PFS and OS showed significant difference between two groups. Toxicity including hematologic and non-hematologic toxicity in S-1 group was little higher than that in observation group(P>0.05), only two patients developed toxicities of National Cancer Institute Common Toxicity Criteria(NCI CTC) Grade 3-4. CONCLUSION Single-agent S-1 sequential chemotherapy therapy following gemcitabine plus S-1 initial first-line therapy is feasible, and extended the PFS and OS, and showed a favorable toxicity profile.