Objective To analyze the clinical effect of self-made Modified Maziren Decoction in the treatment of opioid induced constipation. Methods To select 48 cases of malignant tumor patients with cancer pain who got constipation caused by opioids in our hospital from October 2014 to October 2016. they were randomly divided into two groups， 24 cases in each group. The observation group was treated with self-made Modified Maziren Decoction， and the control group was treated with Lactulose Oral Solution. To compare the clinical curative effect， TCM symptom score， pain control and quality of life between the two groups before and after treatment. Results Compared with the control group， the total effective rate of the observation group was 91.67%， which was significantly improved（P<0.05）. After treatment the first defecation time， each defecation time， defecation interval， defecation difficulty， defecate symptoms score and total score in the two groups were significantly lower than that before treatment（P<0.01）， and the patients in the observation group improved better than the control group（P<0.01）. Compared with before treatment， the digital pain score（NRS）in the two groups were significantly decreased and the KPS score also increased significantly（P<0.01）， and after treatment the pain control and the score of life quality improved significantly better than that in the control group（P<0.01）. Conclusion The self-made Modified Maziren Decoction is effective in treating opioid induced constipation， improving clinical symptoms， reducing the pain of patients， and improving the quality of life.