Objective To investigate the effect of mytomycin C in the operation of dacryocystorhinostomy for curing lacrimal passage obstruction. Method Forty-one patients with traumatic lacrimal passage obstruction were divided into treatment group (n=21, 14 males and 7 females with an average age of 32) and control group. (n=20, 12 males and 8 females with an average age of 35). The patients in treatment group received 0.4mg/ml of mytomycin C when undergoing dacryocystorhinostomy, while the patients in control group received no medicine when undergoing the same operation. Lacrimal passage was cleaned with water after operation, and the operational effectiveness of dacryocystorhinostomy were compared between the treatment group and control group. Results Twenty-one eyes were cured in treatment group, and the cure rate reached 100%. While for the 20 eyes in control group, 17 eyes were cured, and the cure rate was 85%. There existed statistical significance between the two groups (P