ObjectiveTo explore the diagnostic value of “Four-Step Procedure” of laparoscopic exploration in patients with peritoneal metastasis of gastric cancer.MethodsWe retrospectively collected the data of 409 gastric adenocarcinoma patients from July 2016 to August 2020 who underwent “Four-Step Procedure” of laparoscopic exploration in West China Hospital. The descriptive case series study was conducted to analyze the outcome of laparoscopic exploration combined with CY (cytology test), stepwise treatment plans, and the rates of CY1 and P1 (peritoneal metastasis) among cT3–4 patients during different periods. SPSS 22.0 software was used to conduct the univariate and multivariate logistic regression to analyze the high risk factors associated with P1 and (or) CY1.ResultsA total of 409 gastric adenocarcinoma patients who underwent laparoscopic exploration were enrolled in our study. Among them, 65 patients were confirmed to be P1 and (or) CY1. Stratified analysis by cT and cN staging showed that there were 7 (7.4%) and 55 (27.9%) patients with peritoneal metastasis in cT3 staging and cT4 staging, respectively. After laparoscopic exploration, 168 patients received laparoscopic gastrectomy, 35 patients received laparotomy, 143 patients received neo-adjuvant chemotherapy, and 63 patients received conversion therapy. The bar chart showed an ascending tendency in the diagnosis rate of P1 over time among cT3–4 patients. Multivariate logistic regression analysis showed that ascites was an independent risk factor of CY1 and (or) P1 (P<0.001). Additionally, the postoperative complication rate was 2.9% in the patients who merely underwent laparoscopic exploration, including 4 patients with pulmonary infection and 2 patients with urinary retention.Conclusions“Four-Step Procedure” of laparoscopic exploration is reliable and feasible for gastric cancer. “Four-Step Procedure” of laparoscopic exploration has high diagnostic value for peritoneal metastasis of gastric cancer. Our study shows that most of peritoneal metastasis distribute in cT3 and cT4 patients. For these patients, laparoscopic exploration should be recommended to identify if peritoneal metastasis exists and avoid unnecessary laparotomy.