〔Abstract〕 Objective To analyze the serum levels of Pentraxin-3 (PTX-3) and squamous cell carcinoma-associated antigen (SCC-Ag) in patients undergoing chemotherapy after gastric cancer surgery and their clinical significance. Methods 80 patients with gastric cancer treated in the First Affiliated Hospital of Henan University and 112 healthy people in the same period were selected. All patients with gastric cancer underwent postoperative chemotherapy. The levels of PTX–3 and SCC-Ag before and after chemotherapy were measured and compared with healthy people, and the relationship between them and the degree of differentiation and clinical stage was analyzed. Results Serum PTX-3 and SCC-Ag in patients with gastric cancer were significantly higher than those in healthy patients, the difference was statistically significant (P < 0.05); the levels of serum PTX-3 and SCC-Ag in patients with gastric cancer decreased gradually before chemotherapy, 1, 3, and 6 cycles of chemotherapy, the difference was statistically significant (P < 0.05); the serum PTX-3 and SCC-Ag of patients with gastric cancer TNM3 stage were significantly higher than those of TNM2 patients (P < 0.05), and the serum PTX-3 and SCC-Ag expression levels of patients with lowly to moderately differentiated gastric cancer were significantly higher than those of patients with highly differentiated gastric cancer, the difference was statistically significant (P < 0.05); ROC showed that the detection specificity of PTX–3 was 98.75%, which was better than that of SCC-Ag. Both had the same sensitivity and were at a high level, and the area under curve (AUC) of joint detection was the largest. Conclusion The levels of serum PTX–3 and SCC–Ag in patients with gastric cancer decrease after chemotherapy, and are closely related to clinical stage and differentiation.