Abstract: The brake capacity of the explosion-proof rubber wheel vehicle was reduced or even invalid because of the channeling liquid fault of multi-function wet brake of the imported drive axle, safety accidents occur easily. In order to solve this problem, the cause of the failure is found by introducing the structure and principle of brake, and disassembling and analyzing the fault brake. On this basis, the internal structure of brake was improved. The results of theoretical calculation and test verification show that the fault of brake is solved, and the safe hidden trouble of the vehicle is eliminated.