To analyze the influencing factors of major pathological response (MPR) in patients with locally advanced gastric cancer undergoing neoadjuvant immunotherapy combined with chemotherapy and to establish a predictive model. Methods    The clinical data of 48 patients with locally advanced gastric cancer undergoing neoadjuvant immunotherapy combined with chemotherapy admitted to the Department of Gastric Surgery of the First Affiliated Hospital of Soochow University between January 2022 and May 2025 were prospectively collected. The effect of neoadjuvant immunotherapy combined with chemotherapy was evaluated based on the tumor regression grade in postoperative pathology, and the patients were divided into the MPR group (23 cases) and the non-MPR group (25 cases).The parameters before and after neoadjuvant therapy were compared between the two groups. The predictive factors of MPR were analyzed, and a nomogram and Bayesian regression model were constructed. Results  There were significant statistical differences between the MPR group and the non-MPR group in cN stage, the proportion of signet ring cell carcinoma, Lauren classification, CPS  score, ypT stage and ypN stage (P<0.05). Multivariate regression analysis showed early cN stage (OR=0.753, 95%CI 0.430-0.872, P=0.025), non-signet ring cell carcinoma (OR=1.873, 95%CI 1.451-2.314, P=0.043), and CPS≥5 points (OR=2.241, 95%CI 1.692-2.868, P=0.023) was an independent protective factor for predicting MPR. The nomogram model constructed based on the above three factors had a C-index of 0.781 (95%CI 0.613-0.927). The Bayesian regression model showed the area under the ROC curve for predicting MPR was 0.736 (95%CI 0.579-0.883). Conclusion    The nomogram and Bayesian regression model based on cN staging, whether it is signet ring cell carcinoma and CPS score can effectively screen the sensitive population of neoadjuvant immunotherapy for gastric cancer with high clinical application value.