The invention discloses a method utilizing a thermal spraying technique for preparing polyimide coating and a product of the method. The method includes steps of 1, preparing polyimide spray material which is a thermosetting polyimide precursor sizing agent, a thermoplastic polyimide precursor sizing agent or a thermoplastic polyimide powder; 2, performing surface deoiling and roughening on a substrate; 3, sending the spray material prepared in step 1 into thermal spraying flame flow and forming the polyimide coating on the processed substrate surface through spraying. The method is simple in technique, high in efficiency and suitable for field construction. Spray limits of work piece sizes and shapes are removed and the cost is low. The prepared polyimide composite coating can be combined well with the substrate and the microstructures are adjustable. The method can be applied to fields of electrics, mechanics, thermotics, anti-radiation and medical science and the like.