The invention discloses a new preparation method of 4,4-dichlorodiphenyl sulfone. The method comprises the following steps: 1) through using AlCl3 as a catalyst, and chlorobenzene and thionyl chloride as reaction raw materials, performing a Friedel-Crafts reaction at 25-35 DEG C, then hydrolyzing the mother liquor obtained through the Friedel-Crafts reaction, refluxing at 95-100 DEG C for 45-60 minutes, cooling the obtained mother liquor to less than 20 DEG C after refluxing to obtain an organic phase and an aqueous phase; 2) performing reduced pressure distillation on the organic phase, centrifuging, washing the obtained product to be neutral and be used as a product A for later use, wherein the main component of the product A is 4,4-dichlorodiphenyl sulfoxide; and 3) through using the product A and the oxidant hydrogen peroxide as raw materials and acetic acid as satalytic solvent, carrying out an oxidation reaction on the main component 4,4-dichlorodiphenyl sulfoxide of the product A to obtain crude 4,4-dichlorodiphenyl sulfone. Therefore, the existing synthesis method of 4,4-dichlorodiphenyl sulfone is changed, the production cost of 4,4-dichlorodiphenyl sulfone is low, the product quality is good and the reaction time is short.