The invention relates to the field of automobile brake systems, and discloses a power-on electromagnet drum brake. The power-on electromagnet drum brake comprises a brake drum, a first brake pad, a second brake pad, a first brake frame, a first armature core, a first electromagnet core, a first electromagnetic coil, a first outer-circle iron core, a second outer-circle iron core, a second brake frame, a second armature core, a second electromagnet core, a second electromagnetic coil, a third outer-circle iron core, a fourth outer-circle iron core, springs and a fixed shell. The first brake frame is connected with the first brake pad. The first armature core is arranged in the first brake frame. The first electromagnet core is arranged on the outer side of the first armature core, and the first electromagnetic coil is arranged on the surface of the first electromagnet core. The first outer-circle iron core and the second outer-circle iron core are arranged on the two sides of the first electromagnet core. The two ends of each spring are fixed to the first brake frame and the second brake frame. The power-on electromagnet drum brake is simple in structure, easy to control, flexible in braking, rapid in response, and capable of saving electricity and labor.