Polyimide polymer preparation method

The invention relates to a polyimide polymer preparation method. The polyimide polymer preparation method comprises the following steps: dissolving trimellitic anhydride in 1-methyl-2-pyrrolidone; then, adding diphenyl-methane-diisocyanate and a catalyst; controlling proceeding of reaction by the staged heating method to prepare a polyimide polymer, wherein the feeding molar ratio of trimellitic anhydride to diphenyl-methane-diisocyanate is 1:(1-1.2). According to the polyimide polymer preparation method, a one-step synthesis process is adopted, trimellitic anhydride and diphenyl-methane-diisocyanate with a certain ratio are selected in a proper solvent, and under the action of the catalyst, heating reaction is realized by the staged heating method to prepare polyimide. The polyimide polymer preparation method is very simple, dispenses with harsh reaction conditions and excessive reagents and experimental steps, and can adjust the molecular mass of prepared polyimide by controlling the reaction temperature and time.