The invention relates to an electromagnetic core with an extension edge insulating layer, comprising an electromagnetic core and an insulating layer, wherein an insulating layer is also arranged on the outer side end surface of the electromagnetic core, the outer side surface insulating layer is mutually connected with an inner side surface insulating layer, the electromagnetic core is provided with a plurality of grooves, an insulating layer is arranged in each groove and extends outwards to form an extension edge, and the insulating layer extension edge partly covers the end surface of the electromagnetic core. Compared with the prior art, the invention has a structure that the end surface insulating layers are arranged at both ends of the electromagnetic core, the insulating layers of middle grooves form an extension surface through thermal forming, and the extension surface is tightly combined with the end surface insulating layers to enable a contact region of a chip of a motor, a generator or a transformer with an electromagnetic wire to fulfill an insulating function, thereby saving electromagnetic wires, reducing the length of a useless end of an electromagnetic winding, enhancing the efficiency of the motor, the generator and the transformer, and lowering the cost. The invention is suitable for asynchronous motors, DC motors, synchronous motors, series excited machines, servo motors, generators and transformers.