The invention relates to a wall material and a preparation method thereof. The wall material is mainly prepared from cement, polyethylene glycol phase change and heat storage particles, porous silicon oxide, a foaming agent, fly ash, a shrinkage reducer and a modifier according to a mass ratio of (20-30):(10-20):(5-15):(3-8):(30-40):(1-5):(3-8). The preparation method comprises the following steps: preparing a gelling material slurry and foam, mixing the foam with the gelling material slurry to prepare a foam slurry, and carrying out pouring molding to obtain the wall material. The wall material prepared in the invention can effectively reduce the thermal conduction coefficient and the dry density and improve the compressive strength, so the wall material can be used in exterior wall bearing walls, the application range of the wall material is enlarged, and good heat insulating and energy saving effects are realized. Industrial waste fly ash is used as a raw material, so the wall material and the preparation method realize waste recycling, and have high social and economic benefits.