The aim of the present study was to investigate the effect of aspirin on the cell proliferation and migration of gastric cancer cells in p53-knockout mice. Twenty p53−/− male mice aged 6 to 7 weeks, with an average weight of 20±3 g were used. The model of gastric cancer was established by the implantation of a mouse forestomach carcinoma cell line, subcutaneously, at the back of the neck, and then the mice were randomly divided into two groups after establishment of the model (control group, n=10; experimental group, n=10). Aspirin (250 mg/kg) was added to the food in the experimental group one day before model establishment, until the end of the experiment. Mice in the control group were given regular food without aspirin. All mice were sacrificed 3 months afterwards, and gastric cancer tissues were harvested. MTT assay was used to detect the proliferation of the tumor cells. Tumor cell number was also observed. Migration ability was detected by scratch assay, and E-cadherin protein expression was evaluated by immunofluorescence. The results revealed that the proliferation ability of tumor cells in the experimental group was lower than that in the control group. In addition, cell numbers were significantly decreased and the migration ability was diminished. The expression of E-cadherin was also increased in the experimental group, and the differences were statistically significant (P<0.05). In conclusion, aspirin inhibited the cell proliferation and migration of gastric cancer cells in mice.