The invention discloses a novel light-weight high-strength sand-based water-permeable brick and a preparation method thereof. The water-permeable brick comprises, in parts by mass, 100 parts of geopolymer cement, 5-12 parts of a reinforcing agent, 1-10 parts of a thickener, 350-650 parts of high-strength pottery sand, 1.5-3.5 parts of a setting accelerator, 3-5 parts of a coloring agent, 0.5-3.0 parts of a water reducing agent and 15-20 parts of water. Mixing and stirring in a stirrer or a mixer are performed multiple times, and then the obtained mixture is placed in a brick making machine for vibration molding. Steel slag, fly ash and other large solid waste are utilized, and the defects of easily blocked pores, short water-permeable effective period and large density of existing water-permeable bricks are overcome. The prepared water-permeable brick has good water permeability, long water permeable effective period, high compressive strength and low density, and can be widely applied to sponge cities and other municipal engineering construction, the utilization added value of steel slag and other large solid waste is improved, and the ecological environment is protected.