The invention provides a composite shape-stabilized phase change material. The phase change material is a crystallized hydrated salt phase change material, and a support material is meerschaum. A preparation method of the phase change material comprises the following steps: performing acid treatment, high-temperature treatment and organic treatment on the meerschaum in sequence; performing an adsorption reaction on the treated meerschaum and a saturated aqueous solution of a crystallized hydrated salt under a vacuum condition to obtain a novel composite shape-stabilized phase change material. The composite shape-stabilized phase change material has the advantages that 1) packaging and shape stabilizing of the phase change material are realized through the porous structure of the meerschaum, the loss of phase change material crystal water is limited successfully through a functional group of the meerschaum, phase separation is reduced, and the crystallization performance and phase change energy storage feature of the crystallized hydrated salt phase change material are ensured; 2) raw materials of the support material and the phase change material are low in prices and readily-available; the composite preparation method is simple and convenient. By adopting the composite shape-stabilized phase change material and the preparation method, the phase separation phenomenon, overcooling phenomenon and leakage are reduced, and the stability of the phase change material in a long-term use process is improved; the phase change material has a wide application prospect in the phase change heat storage field.