The invention discloses a method for preparing artificial stone by use of unsaturated polyester paint waste. The method comprises the following steps: uniformly mixing raw materials of the bottom layer, the toughening layer and the surface layer of artificial stone; sequentially pouring, shaping and curing to obtain artificial stone. The bottom layer and the surface layer of the artificial stone comprise the following raw materials in parts by weight: 20-75 parts of unsaturated polyester paint waste powder, 0-35 parts of a flame retardant, 10-20 parts of quartz sand, 10-25 parts of unsaturated polyester resin, 0-3 parts of a curing agent, 0-2 parts of a hindered amine additive, 0-2 parts of a promoter, 0-1 part of a coupling agent A and 0-2 parts of a catalyst A. The artificial stone is wide in application, can serve as indoor artificial stone decorative patterns, kitchen countertops, artificial stone window sills, artificial stone external wall decorative boards and the like, has the advantages of small density, hard texture, good flame retardancy, excellent aging resistance and the like, particularly, has the weight of 1/2-1/3 of that of ordinary artificial stone under the condition of the same strength, and is convenient to construct and mount.