Objective To investigate the association between the longitudinal dynamics of serum total protein TP and postoperative survival outcomes in patients undergoing radical gastrectomy for gastric cancer. Method Patients with adenocarcinoma of the stomach or gastroesophageal junction who underwent D2 radical surgery between 2010 and 2022 were enrolled. Longitudinally measured TP levels during follow-up were recorded and patient survival status and duration were ascertained via cause-of-death verification or telephone follow-up. Cluster analysis of oncological characteristics was performed using the K-prototype algorithm. In the joint model a linear mixed model was adopted for the longitudinal sub - model and a Cox proportional hazards model was used for the survival sub - model. This joint model aimed to explore the interaction between TP and oncological characteristic subgroups analyze the impact of temporal trends in TP changes during follow-up on survival and dynamically predict individual survival probabilities. Result A total of 601 patients were enrolled with a median follow-up duration of 5. 74 years. Among these 438 patients were followed up until death with a median survival time of 2. 18 years. Cluster analysis revealed two oncological characteristic clusters cluster A was featured by more advanced tumor stages poorer differentiation and an increased risk of neural and vascular invasion. The joint model demonstrated that the interaction between oncological characteristic subgroups and time - varying TP levels represents a critical determinant of postoperative survival. Notably a negative association was observed between TP levels and mortality in cluster A. Conclusion Serum TP levels following radical gastrectomy for gastric cancer exhibit a subgroup - specific negative association with mortality. Regular monitoring of TP may offer valuable insights for optimizing nutritional support and prognostic management.