The utility model relates to the field of an engine, and specifically relates to an electromagnetic conversion DC engine converting electromagnetic energy into mechanical energy. A DC power supply of the engine is connected with a commutator (10) through a lead, the commutator (10) and rotary discs (3) are mounted on a main shaft (2), magnetic sheets (4) are evenly distributed on outer circumferential surfaces of the rotary discs (3), coils (5) are mounted outside the outer circumferential surfaces of the rotary discs (3) through a support and connected with the commutator (10) through leads, gaps are disposed between the coils (5) and the magnetic sheets (4), the other end of the main shaft (2) is connected with a load, and the main shaft (2) is mounted on a machine base (11). The diameter of each rotary disc (3) is large, and an angle difference is provided between each two adjacent rotary discs (3), so output powers of the rotary discs (3) compensate each other, the starting torque and the starting power of the engine are improved, the fact that larger power is generated from smaller electric energy input is thus realized according to potential energy of a magnetic field and the lever principle, and an object of energy consumption reduction is achieved.