Abstract: Objective To analyze the clinical value of multi-slice spiral CT in differential diagnosis of diffuse malignant peritoneal mesothelioma(MPM), tuberculous peritonitis and peritoneal metastatic carcinoma. Methods The clinical materials of 93 patients with diffuse MPM or tuberculous peritonitis or peritoneal metastatic carcinoma from September 2015 to October 2019 were retrospectively analyzed, and they were divided into diffuse MPM group(n=27), tuberculous peritonitis group(n=32)and peritoneal metastatic carcinoma group(n=34). The differences of multi-slice spiral CT imaging were analyzed among the three groups, including the location of the lesions, the water density of the abdominal layer(CT value greater than 20 HU indicated high-density ascites), the degree of peritoneal thickening, the way of enhancement, and the size of lymph nodes. Results There were no significant differences in pathological distribution and ascites volume among the three groups(P>0.05). There were significant differences in ascites density, parietal peritoneum, lymph nodes and edge of lesions among the three groups(P<0.05). Conclusion Multi-slice spiral CT shows a certain clinical value in differential diagnosis of diffuse MPM, tuberculous peritonitis and peritoneal metastasis carcinoma.