Objective To observe the clinical value of systemic inflammatory immunity index(SII) and red blood cell distribution width (RDW) in screening for gastric cancer. Methods Retrospective analysis was performed to collect baseline data from 81 patients with gastric cancer admitted between January 2020 to December 2021, and baseline data from 84 patients with gastric mucosal precarcinoma during the same period,collect each patient’s RDW, platelet count, neutrophil count and lymphocyte count in peripheral blood, and calcuate systemic immune inflammation index (SII)。SII was calculated according to the formula [SII= neutrophil count (×109/L) × platelet count (×109/L)/lymphocyte count (×109/L)].Use logistic regression to analyze the relationship between SII and RDW in peripheral blood and gastric cancer patients,and draw curve ROC to analyze the predictive value of SII and RDW in peripheral blood for gastric cancer. Results The results showed that RDW and SII in peripheral blood between gastric carcinoma group and gastric mucosal precarcinoma group ,the differences were statistically significant (P < 0.05), but no significant differences in other baseline data between groups (P > 0.05).All independent variables were included in the established regression model for binary logistic regression analysis. The results showed that high expression of RDW and SII in peripheral blood was a risk factor for gastric cancer in patients with gastric mucosal precarcinoma (OR > 1, P < 0.05).The ROC curves were plotted,and the results showed that the AUC of peripheral blood SII and RDW levels in predicting gastric cancer were 0.944 and 0.677, respectively, which had certain predictive value.Conclusion SII and RDW in peripheral blood are important in the clinical diagnosis of gastric cancer. expression of PGR and high expression of RDW may suggest a higher possibility of gastric cancer, and can be used as an early predictor of gastric cancer patients,high expression of SII and RDW may indicate a higher possibility of gastric cancer, which can be used as an early predictor of gastric cancer.