The invention relates to a brake automatic cooling method and a device on the basis of automobile air conditioner; wherein, the method comprises the steps as follows; the refrigeration system of the automobile air conditioner is connected in parallel with a cooling circuit and the air cooling is carried out for the brake automatically by a control system; the device comprises a compressor, a condenser, a filter/drier which are sequentially connected one after another by pipelines; the output pipeline of the filter/drier is provided with an air three-way inlet; one branch of the air three-way inlet is connected with a first evaporator by a first electromagnetic valve and a first temperature adjusting expansion valve; the another branch of the air three-way inlet is connected with a second evaporator by a second electromagnetic valve and a second temperature adjusting expansion valve; the output pipelines of the first evaporator and the second evaporator are commonly connected backwardson the compressor by an air three-way outlet. The control system comprises five branches which are grounded in parallel and respectively control the cab and the brake by an A/C linking switch and a brake switch. By a group of cooling circuit in parallel, the method and the device of the invention lead the system to respectively refrigerate the cab and the brake, thus achieving the object of gaining the requirement.