The invention discloses a preparation method of bismuth tungstate/graphene photocatalyst with a broad-spectrum degradation property. The preparation method particularly comprises the following steps: (1) dissolving 0.97 g of Bi(NO3)3.2H2O in 50 ml of a glacial acetic acid solution via stirring, adding 0.0017 to 0.034 g of oxidized graphene into the obtained solution, carrying out ultrasonic dispersion for 1 hour to obtain a solution X; (2) dissolving 0.33 g of Na2WO4 in 20 ml of water via stirring to obtain a transparent clear solution Y; (3) adding the transparent clear solution Y into the solution X, carrying out stirring for 10 min, controlling the pH of the reaction system to be lower than 2 with glacial acetic acid, transferring reaction products into a closed polytetrafluoroethylene reaction kettle after the pH is stable, and heating the reaction kettle to be 180 DEG C for 3 hours to obtain the bismuth tungstate/graphene photocatalyst. The bismuth tungstate/graphene photocatalyst prepared according to the method can be used for effectively degrading rhodamine B and methyl orange dye wastewater, sulphanilamide and sulfamonomethoxine pharmaceutical wastewater, and phenol wastewater when being exposed in the sun, is nontoxic, efficient, cheap, and suitable for a broad spectrum, and has a relatively high market application prospect.