Abstract: Objective To study the value of carbohydrate antigen 125 （CA125） level measurement in diagnosis and treatment of tubercular peritonitis. Methods Serum CA125 and ascites levels were measured in 35 patients with tubercular peritonitis and 28 patients with electrochemiluminescence method. The results were compared with those measured in non-active pulmonary tuberculosis and control groups. Results The serum CA125 level was 243.29±131.60U/mL and 309.05±245.38U/mL in tubercular peritonitis group and malignant ascites group, respectively, with no statistical difference between the 2 groups （P＞0.05）. However, the serum CA125 level was significantly higher in both tubercular peritonitis and malignant ascites groups than in control group （7.13±4.50U/mL, P＜0.01）. The ascites CA125 level was 590.17±275.18U/mL and 732.39±362.56U/mL in tubercular peritonitis group and malignant ascites group, respectively, with no statistical difference between the 2 groups （P＞0.05）. However, both serum and ascites levels were as high as 74.6% in tuberculosis peritonitis group. Six months after anti-tuberculosis treatment, the serum CA125 level in tubercular peritonitis group was decreased to 8.47±5.28U/L, compared to that in control group （7.13±4.50U/mL, P＞0.05）. Conclusion The value of CA125 in diagnosis of tubercular peritonitis is limited. However, dynamic observation of changes in CA125 level may help to evaluate the prognosis of patients with tubercular peritonitis.