Abstract: Objective To investigate the efficacy of the combination injection of lentinan and urokinase for the treatment of malignant serous cavity fluidify. Methods Seventy-two patients with malignant serous cavity fluidify were randomly devided into treatment group (36 patients) and control group (36 patients). The canal of Cuvier was inserted into the serous cavity to drain the fluidity within 2 to 3 days, and the drugs were given by intracavitary injection. Then 8 to 10 mg of lentinan and 1 10⁵ to 15 10^5 U of urokinase were injected into the treatment group once a week for 4 weeks. While 60 to 80 mg of DDP was injected into the control group once a week for 2 weeks. Hydration and stopping expectoration treatment were given to the control group during the treatment peroid. Results The effective rate for the treatment group (83.3 %, 30/36) was higher than that of the control group (61.1 %, 22/36). Thus the effective rates between the two groups of patients showed significant difference (P<0.05). The improvement rate of performance status KPS Score for the treatment group (72.2%, 26/36) was higher than that of the control group (61.1 %, 22/36), which also showed significant difference (P＜0.005). Conclusion The intracavitary combination injection of Lentinan and urokinase is effictive and safe for the treatment of malignant serous cavity fluidify. This method was worth to be polpularized in clinic due to the improvement of the life quality for the patients after the treatment.