The invention provides a preparation method of a composite phase change material and a preparation method of leather added with the same. In the preparation of the composite phase change material, tetraethoxysilane is added and pH value is adjusted to acidity, thus silicon dioxide with a microcellular structure is decomposed by tetraethoxysilane. The composite phase change material can adopt silicon dioxide as a supporting material and liquid polyethylene glycol is absorbed into the microcellular structure through capillary forces. When polyethylene glycol is converted into liquid, polyethylene glycol difficultly overflows from micropores, thereby polyethylene glycol is unneeded to be filled in a container and the cost is reduced. When the composite phase change material is added to leathers, the composite phase change material has favorable functions of adjusting temperature.