The invention discloses a high-strength waterproof plaster brick and preparing method, which comprises the following parts: 40-90 percent plasters dihydrate, 10-60 percent hydraulic gelling material and 1-10 percent booster. The preparing method comprises the following steps: dispensing; grinding; sieving; blending; doping water; stirring; vibrating; pressing or squeezing into moulding; curing through steam. The invention uses large scale of industrial waste in the smelting or chemical manufacturing course as raw material, which reduces waste from polluting environment.