The invention provides a new preparation method of an anti-gout medicine Lesinurad and its key intermediate. By using the process provided by the invention, a compound IV can be directly converted into a product III without separation, the reaction yield is greatly increased, and the operation step can be simplified. In addition, the synthesis of the novel intermediate provided by the invention does not require the high-toxicity thiophosgene and carbon disulfide, which greatly improves the safety and environmental protection of the process. The novel synthesis preparation process of Lesinuradis highly efficient, economical, safe, environmentally friendly and suitable for industrial production. In the specification, wherein R is cyclopropane, halogen, trifluoro mesylate, mesylate, and p-toluenesulfonate, and preferably R is cyclopropane; R3 represents COCH3, or R3 represents benzyl or CH2R4, wherein R4 represents an ester group, CN, CH2OH or a phenyl group substituted with one or moreselected from C1-C6 alkyl group and halogen; and X is a halogen.