Provided is a method for preparing 2-hydroxy-4-(2,3-disubstituted benzyloxy)-5-substituted benzaldehyde derivative represented by formula (I). The method comprises the following steps: (1) preparing 3-aryl-2-substituted toluene derivative 2 by using 3-iodo-2-substituted toluene derivative 1 and aryl boronic acid 5 or aryl boronate as starting materials; (2) preparing a benzyl halide derivative 3 by using 3-aryl-2-substituted toluene derivative 2 as starting materials; and (3) preparing 4-(2, 3-disubstituted benzyloxy)-2-hydroxy-5-substituted benzaldehyde derivative (I) by using benzyl halide derivative 3 and 2,4-dihdrox-5-substituted benzaldehyde 6.