Objective To investigate the characteristics and diagnostic value of spiral CT three phase enhanced imaging in gastric cancer. Methods 50 patients with gastric cancer treated in our hospital from January 2015 to December2016 were selected,the clinical data and imaging data of 50 patients were collected, analysis of 50 cases of gastric cancer patients with CT scan and CT three phase enhanced scan image performance, the detection rate and diagnostic accuracy of CT plain scan and CT three phase enhanced scan were compared with the pathological examination results as the standard. Results The detection rate and diagnostic accuracy of CT scan in gastric body and gastric antrum were significantly lower than those of CT three phase scan,the difference was statistically significant (P<0.05). The total detection rate and diagnostic accuracy of CT scan for gastric cancer were 74.00% and 50%, which were significantly lower than those of CT three, 98.00% and 96.00%, and the difference was statistically significant (P<0.05). CT scan images of patients showed different degrees of thickening, thickening of gastric wall was extensive natural radian, gastric wall stiffness, the stomach contour is not clear, the surrounding fat layer fuzzy or disappear completely. In the three phase of CT enhancement, the contrast gradient in gastric antrum and gastric wall was better, which can directly display the size, shape and adjacent tissue structure of tumor, in 36 patients, the thickened wall of stomach showed uneven changes, and the masses in the stomach were prominent inside and outside the cavity, which could directly invade the surrounding tissues. The medial mucosa lesions in 41 patients showed obvious enhancement, portal phase area increased and the equilibrium period completely enhanced. Conclusion Spiral CT three phase enhanced scan can clearly display the image features of gastric cancer lesions,the detection rate and diagnostic accuracy are high, which can provide reliable imaging data for clinical treatment.