The invention provides an insertion device for motor stator slot insulation paper. The device comprises a rack, an unreeling device, a heating device, an indentation device, a preforming device, a first forming device, a paper feeding device, a corner cutting device, a paper inserting device, a cutting-off device, a second forming device, a dividing device, a stator positioning device, and an electric appliance cabinet assembly. Through dividing a one-step forming process of insulation paper into multistage forming, forming internal stress of the insulation paper is released in each forming process, and in repeated heating and forming processes, stability of the formed insulation paper is ensured. The insertion device is driven by a servo motor, length of paper feeding of the insulation paper can be accurately controlled, and when motor stack thickness changes, just a setting value of paper feeding length needs regulating. The device is simple and convenient in operation, reduces length error of insulation paper feeding, and reduces errors of insulation paper length and motor stack thickness and height after the insulation paper is inserted, so as to improve integrated performance of a motor.