Disclosed are a hydroxy containing polypropylene and a preparation method thereof. The weight content of the hydroxy group in the hydroxy containing polypropylene is 1-20%. The preparation method specifically comprises the following steps of, firstly, chlorinating isotactic polypropylene at 110-130 DEG C with an aqueous reaction solution, and controlling the added mount of chlorine to obtain chlorinated polypropylene, wherein the chlorination rate of the dried chlorinated polypropylene is 1-40%; secondly, dissolving the chlorinated polypropylene obtained in the first step into solvent at 60-120 DEG, then sequentially adding in hydroxy containing acryl compounds, hydroxy protecting agent and catalysts for reaction at 60-120 DEG C for 1-10 h, cooling down, filtering out the solvent, sequentially washing reaction products with diluted hydrochloric acid solution and then sodium bicarbonate solution until to be neutral, and drying the reaction products to obtain the hydroxy containing polypropylene. The preparation method of the hydroxy containing polypropylene is simple in process and high in operability, solves the problems of expensive catalysts, complicated process equipment, strictreaction conditions and the like of methods such as plasma method, noble metal catalyzed method and biological method, and greatly improves the dyeing property and the biocompatibility of polypropylene.