Objective To explore risk factors for postoperative infection in patients with gastric cancer, and provide evidence for prevention and control of infection. Methods A retrospective survey was conducted among patients with gastric cancer who underwent radical gastrectomy in Gansu Provincial Hospital from 2012 to 2018, survey was conducted with a self-designed questionnaire, patients' medical records were reviewed, basic characteristics of patients, operation-related conditions, infection status and so on were surveyed. Patients were divided into infection group and non-infection group according to whether they had postoperative infection or not, clinical parameters were compared and risk factors for postoperative infection were analyzed. Results A total of 427 patients underwent radical gastrectomy, 60 in infection group and 367 in non-infection group. Postoperative infection rate was 14.05%, respiratory tract infection was the main infection, accounting for 41.67%. 60 patients were isolated 63 strains of pathogenic bacteria, mainly gram-positive bacteria (n=34, 53.97%). Gram-positive bacteria were mainly Streptococcus viridans (n=19), and 5 strains of methicillin-resistant Staphylococcus aureus (MRSA) were also isolated. Among 60 patients with postoperative infection, 44(73.33%) were infected with single pathogen, 9 (15.00%) with two pathogens and 7 (11.67%) with three pathogens. Univariate analysis showed that smoking, peptic ulcer, resection site, preoperative hospital stay, duration of operation, postoperative bed rest time, duration of venous cathe-terization and total hospital stay were influencing factors for postoperative infection in patients with gastric cancer (all P<0.05). Logistic regression analysis showed that history of underlying diseases of peptic ulcer (OR, 2.577[95%CI, 1.193-5.568]) and long duration of hospital stay before operation (OR, 2.227[95%CI, 1.079-4.599]) were independent risk factors for postoperative infection in patients with gastric cancer. Conclusion Incidence of post-operative infection in patients with gastric cancer in this hospital is high, health care workers can take effective preventive and control measures against the related risk factors, especially control of underlying diseases of peptic ulcer before operation and pre-operative hospital stay.