The invention provides a wall building material and a preparing method thereof, and relates to the field of building materials. The wall building material is prepared from, by weight, 55-70 parts of abandoned ceramic materials, 45-60 parts of rock wool board waste materials, 10-20 parts of straw waste residue, 10-15 parts of anti-crack fiber, 10-15 parts of calcium carbonate powder, 15-20 parts of perlite, 12-16 parts of diatomite powder, 0.5-1.5 parts of defoaming agent, 0.5-1 part of mortar water-retaining agent, 0.2-0.5 part of water reducing agent,10-14 parts of mineral wool, 30-40 parts of vermiculite, 5-10 parts of water, and 2-4 parts of dispersing agent. The preparing method of the wall building material comprises the first step of weighing, by weight, the abandoned ceramic materials, the rock wool board waste materials, the straw waste residue, the anti-crack fiber, calcium carbonate powder, perlite, diatomite powder, the defoaming agent, the mortar water-retaining agent, water reducing agent, the mineral wool, and vermiculite into an agitator to be stirred so that a solid mixture can be obtained; the second step of adding the water and dispersing agent into the solid mixture, and stirring the mixture for 20-30 min to make the mixture mixed uniform. The wall building material has the advantages of being good in heat preservation and heat insulation effect, high in intensity, high in waste reutilization rate, good in sound absorption effect, and high in corrosion resistance.