The invention discloses a composite heat storage material and a preparation method thereof. The composite heat storage material is prepared by adopting hematite ore as main material, bauxite tailing as forming material and clay as auxiliary material and adding water to mix. The proportioning of the materials is that the contents of hematite ore, bauxite tailing and clay are separately 70-87%, 7-15% and 6-15%. The preparation method comprises the following steps: firstly mixing the materials: mixing tailing and clay evenly, adding water for soaking, then adding hematite ore to mix, placing the mixture in a ventilated place while controlling the moisture content; then shaping: placing the mixed materials in moulds to form and prepare test blocks; then drying: placing the test blocks in a oven to dry; finally roasting and cooling to obtain the heat storage material. The specific heat of the heat storage material is 0.150-0.166cal-g<-1>-K<-1> and the thermal conductivity is 1.18-1.30W-m<-1>-K<-1>. The preparation method of the heat storage material is characterized by easy process, low cost, higher value of mineral tailing and the like and the prepared composite heat storage material has high specific heat and good heat conductivity.