Although gastric cancer (GC) is most common in the elderly population, the rate of early-onset gastric cancer (EOGC) is increasing each year. In this study, the clinicopathological information of 9,406 patients who underwent GC resection in our institution from 2000 to 2019 was collected. We compared the clinicopathological characteristics between the EOGC group, in which patients were younger than 40, and the control group, summarizing the evolutionary trends of the EOGC group's characteristics. Then, we focused on the characteristics of EOGC in different sex groups and the evolutionary trends of female EOGC patients' clinicopathological characteristics. The results showed that a greater proportion of the EOGC group was female (47.32% vs. 23.53%), had poorly differentiated adenocarcinoma (84.78% vs. 64.11%), gastric antrum cancer (59.38% vs. 50.72%) and signet ring cell carcinoma (21.13% vs. 8.51%). Over the past 20 years, the proportion of EOGC patients with T4 stage (10.71% to 41.74%), N3 stage (0 to 30.73%) and poorly differentiated adenocarcinoma (70.37% to 92.23%) has increased. In the female EOGC group, there were more patients with stage III-IV disease (57.23% vs. 43.22%), T4 stage (35.85% vs. 22.60%), and poorly differentiated adenocarcinoma (91.88% vs. 78.68%). Additionally, the proportions of T4 stage (16.13% to 50.50%), N3 stage (0% to 31.68%), and poorly differentiated adenocarcinoma (69.23% to 98.97%) gradually increased. In conclusion, our study not only identified unique clinicopathological characteristics of EOGC but also revealed the evolutionary trends of these indicators, which may provide some theoretical basis for the prevention and diagnosis of EOGC.