Objective To investigate the relevance among sarcopenia, peripheral inflammatory, and nutritional factors, as well as the impact of sarcopenia on the prognosis of gastric cancer. Methods A total of 174 patients with gastric cancer in Department of Gastrointestinal Surgery in West China Hospital of Sichuan University from July 2016 to December 2020 were retrospectively included. The skeletal muscle index (SMI) of the third lumbar vertebra level was calculated using CT images, and male patients with SMI<52.4 cm2/m2 and female patients with SMI<38.5 cm2/m2 were considered sarcopenia. The key clinicopathological features of patients were collected for prognostic analysis. ResultsAmong the 174 patients with gastric cancer, 73 patients (41.95%) were diagnosed with sarcopenia. Compared with those of non-sarcopenia, the patients who were diagnosed with sarcopenia showed a significantly elder age and lower body mass index (BMI). In addition, males demonstrated a significantly higher rate of sarcopenia. Further, patients with sarcopenia showed a significant increasing in the incidence of postoperative pulmonary infections and length of hospitalization than patients without sarcopenia. The two groups showed significant differences in type 2 diabetes, peripheral C-reaction protein (CRP), interleukin-6 (IL-6), albumin, prealbumin, and hemoglobin. Overall, the multivariate analysis and Kaplan-Meier survival curves indicated that sarcopenic patients had a significantly lower survival rate than the non-sarcopenia patients. Conclusion Sarcopenia is closely related to higher levels of inflammation, malnutrition, and poor prognosis in patients with gastric cancer. Therefore, we should diagnose sarcopenia patients as early as possible, and give nutritional support to the patients.