The invention discloses a preparation method of a coated 
thermal battery composite electrode sheet. The 
composite electrode sheet is composed of a heating layer, a positive 
electrode layer and a separator layer. For the preparation method, firstly, a layer of 
fiber mesh is laid on a conductive substrate, a positive 
electrode layer is then coated, after 
drying, an 
asbestos mesh is placed on a surface of the positive 
electrode layer; secondly, the separator layer is then coated on the positive electrode layer on which the 
asbestos mesh is placed, after the separator layer is dried, the heating layer is coated on the other side of the conductive substrate to obtain a composite sheet; and thirdly, high temperature resistant waterproof conductive 
adhesive is coated on both sides of the composite sheet, after 
drying, the composite positive electrode layer is obtained. The 
composite electrode sheet is advantaged in that thickness of the composite electrode sheet can be adjusted according to height of a scraper in the preparation process, so the thickness of the composite electrode sheet is precisely controlled, the composite electrode sheet is combined with a 
thermal battery negative electrode LiB sheet with controllable thickness to form an ultra-thin 
thermal battery cell, the obtained composite electrode sheet has a function of preventing 
moisture absorption and preventing a diaphragm from being melted and overflowing, and the preparation method has advantages of high 
chip rate and simple process and meets requirements of 
engineering use.