The invention belongs to the field of automobile braking energy recycling, and particularly relates to a braking power generating mechanism based on air compression. The braking power generating mechanism comprises a brake disc, brake disc protrusions, a brake mechanism support, a brake energy mechanical conversion mechanism, brake plate supports, hydraulic columns, a power generator, an air motor, compression cylinders, an air tank and pistons. The brake plate supports are arranged on the brake mechanism support. When the brake disc rotates, in the initial stage of the brake process, brake plates are gradually close to the brake disc, an ejector block is in contact matched with the protrusions firstly, the ejector block linearly moves in a reciprocating manner in the direction of a cylinder guide rail, the pistons are driven to reciprocate through cooperation, and accordingly the air motor is driven to drive the power generator to generate power. In the later braking stage, the brake plates start to make contact with the brake disc, larger friction force is generated, and wheels are forcefully braked. By means of cooperation of the ejector block and the protrusions, braking energy is converted into reciprocating movement, the air motor is driven to drive the power generator to generate power accordingly, the brake energy can be effectively utilized, and the energy saving effect of an automobile is improved.