The invention relates to a preparation method of a paraffin-silicon dioxide composite phase change energy storage material. The adopted technical scheme is as follows: uniformly stirring diatomite, anhydrous ethanol and water at the temperature of 60 DEG C, adjusting the pH value of a system to about 3, and stirring for 80-100min to form a SiO2 sol; taking paraffin, distilled water and an emulsifying agent, heating and stirring at the temperature of 50-70 DEG C for 20-40min to obtain an emulsion; mixing the SiO2 sol and the emulsion according to a certain weight ratio of 1: (1.5-2.5), heating and stirring at the temperature of 50-70 DEG C for 80-100min, putting a solution after the reaction into an oven, and drying at the temperature of 70-90 DEG C to obtain a target product. According to the preparation method provided by the invention, the paraffin is embedded into a three-dimensional network of SiO2, so that the problem of liquid flow of the paraffin during application of a heat accumulation technology is inhibited; and the paraffin-silicon dioxide composite phase change energy storage material provided by the invention has the characteristics of good heat preservation performance, high phase change latent heat and good chemical stability.