The Modular brake valve is composed of reducing valve, unloading valve and reciprocating valve.The reducing valve reduces the hydraulic oil pressure from the rear brake accumulator , and the unloading valve regulates the pressure ,which provides the residual pressure in the rear brake pipeline after passing through the reducing valve,reciprocating valve provides residual pressure for rear brake line according to plunger position, after the pedal valve or retarder valve is actuated, the brake actuation pressure overcomes the residual pressure and produces braking effect on the rear brake disc.