Abstract: Background and purpose: Primary gastric diffuse large B-cell lymphoma (PG-DLBCL) is the most common histological subtype of gastric lymphoma, lacking specific clinical manifestations, and it is confused with gastric cancer, ulcer or other inflammatory lesions upon endoscopic examination. The pathological and histological manifestations are complex, and it is difficult to diagnose PG-DLBCL. This study aimed to explore the clinicopathological features of PG-DLBCL and analyze the prognostic factors and survival rate. Methods: The clinical and pathological data of 104 PG-DLBCL patients admitted to the Second People’s Hospital, Changzhou City from January 2008 to July 2018 were retrospectively analyzed. The chi-square test was used for the comparison of counting data between the two groups. Kaplan-Meier method was used to calculate the survival rate and draw the survival curve. The Log-rank test and COX regression model were used for the analysis of single and multiple prognostic factors. Results: There were 104 PG-DLBCL patients, including 45 males and 59 females. The median age of onset was 68 years. All 104 patients were followed up for 6.0-103.0 months. The median follow-up time was 71.0 months. The median survival time was 56.8 months. The 1-year, 3-year and 5-year overall survival rates were 90.1%, 76.8% and 47.6%, respectively. Pathological classification: 40 cases of germinal center B cell-like (GCB) and 64 cases of non-germinal center B cell-like (non-GCB). The results from fluorescence in situ hybridization (FISH) detection showed that there were 27 cases of c-Myc gene abnormality (accounting for 26%, among which 17 cases had multiple copies and 10 cases had rearrangements), 26 cases of B-cell leukemia/lymphoma 2 (BCL-2) gene abnormality (accounting for 25.2%, among which 17 cases had multiple copies and 9 cases had rearrangements), 32 cases of BCL-6 gene abnormality (accounting for 31%, among which 23 cases had multiple copies and 9 cases had rearrangements). The results of single-factor analysis showed that serum CA125 level, serum lactate dehydrogenase (LDH) level, international prognostic index (IPI) score, modified Ann Arbor stage, bone marrow invasion, treatment method, pathological non-germinal center subtype and BCL-2/ BCL-6/multiple myeloma protooncogene-1 (MUM-1)/cell division cyclin 7 (CDC7)/minichromosome maintenance protein 2 (MCM2) protein expression level were all related factors affecting the prognosis of PG-DLBCL patients (P＜0.05). Multi-factor analysis results showed that the improved Ann Arbor clinical stage ⅢE-ⅣE, IPI grade 2 or more, pathological type of germinal center subtype, high CDC7 protein expression, MCM2 expression, FISH detection of the BCL-2 gene rearrangement were independent risk factors for the prognosis of patients with PG-DLBCL. Conclusion: The onset of PG-DLBCL is mainly in the elderly, with no particularity in clinical manifestations. Endoscopic detection rate is high, and the diagnosis depends on pathology. R-CHOP (rituximab, cyclophosphamide, hydroxydaunomycin, oncovin and prednisone) chemotherapy is the preferred treatment method.