Down-hole motor is a kind of downhole drilling tool powered by mud. The mud from mud pump enters motor by way of bypass valve, and a pressure drop between motor inlet and outlet created, such pressure drop will drive the motor rotator to rotate, and transmit the torque and rotary speed to bit by universal shaft and transmission shaft. The downhole motor property mainly depends upon its property parameters. This product uses the high and new technology of coating to avoid coating off of rotors resulted from the traditional technology. Its strength and life are greatly improved. It is applicable to directional drilling horizontal drilling, composite drilling, cluster wells, sidetrack wells and well workover etc.