The utility model provides an air-to-liquid conversion brake clamp unit. The unit comprises a cylinder mounting seat, a hydraulic cylinder and a clamp assembly. A piston rod is arranged in the cylinder mounting seat movably in a penetrating mode, a service braking piston is connected with one end of the piston rod in the cylinder mounting seat, a service braking cylinder is connected into the cylinder mounting seat, a service braking piston is sealed in the service braking cylinder movably, and an air inlet is formed in the service braking cylinder. The hydraulic cylinder is connected onto the cylinder mounting seat and comprises a piston cavity, and one end of the piston rod penetrating the cylinder mounting seat penetrates the piston cavity movably. The clamp assembly comprises two opposite clamp bodies which are connected with the hydraulic cylinder respectively, a brake pad carrier is arranged on the opposite sides of the two clamp bodies respectively, and pressure cavities are formed between the brake pad carriers and the clamp bodies and communicated with the piston cavity. By means of the unit, common air pressure is converted into liquid pressure to be acted on a brake disc finally,, and large brake output force can be achieved.