The invention discloses a solvothermal preparation method for a visible-light photocatalyst Bi2WO6 nano structure. The steps are as follows: (1) solvothermal reaction solution is prepared: according to a certain proportion, bismuth salt and tungsten salt are dissolved in polyol solvent to form clarified solution, and a moderate amount of mineralizer is added in the solution and uniformly mixed; (2) under the temperature ranging from 120 DEG C to 240 DEG C, reaction takes place under a solvothermal condition for 10 to 30 hours; (3) precipitate is centrifugally separated from solvothermal reaction product, cleaned and dried in the air with the temperature of 50 DEG C to 200 DEG C; (4) the Bi2WO6 prepared by the solvothermal method is of a flower-like nano hiberarchy formed by quantum dots and nano sheets. The method has the advantages of simple technique and low cost, and the prepared Bi2WO6 nano structure has good crystallinity, a large specific surface area and high-efficient visible-light photocatalysis performance.