A direct current motor comprises a rotor, a stator, a brush reversing device fitted on a rotary shaft of the rotor, a plurality of pairs of magnetic poles fitted on the stator. Said rotor is further provided with an armature winding in its iron core. The magnetic pole is combined by permanent magnet and exciting winding. Based on the formula: M=C Phi Ia, wherein M is torque, C is constant, Phi is magnetic flux and Ia is armature current, the Phi of the combined magnetic pole is controlled to allow the motor to output different torques according to the practical loading condition. The utility model incorporates the advantages of both permanent-magnet motor and current excited motor, and is adaptive for the controllable adjustment upon unstable loads to reduce high-current operation under overload, thereby optimizing work environment and increasing service life of motor and battery.