The aim of this study was to investigate the variation of the friction coefficient of heat sealable film during the solvent-free compounding process. The variation rule of the friction coefficient was studied from three aspects, including the film thickness of the heat sealable layer, the formula of the heat sealable film, and curing process control. The thicker the heat sealable film used for solvent-free compounding, the smaller the variation of the friction coefficient. In practical production, the thickness of the heat sealable film must be above 35 μm, in order to control the variation of the friction coefficient. Application of heat sealable film with good anti-migration properties could slow down the increase of the friction coefficient, and the temperature change during the production had great influence on the variation of the friction coefficient. In order to improve the friction coefficient of solvent-free compounding, the slipping agent formula, the structure of heat sealable film, and the solvent-free compounding technology should be improved to control the friction coefficient of the solvent-free composite product below 0.25.