A method for preparing 2-mercaptobenzothiazole where the aniline method is adopted to perform reaction in the presence of a catalyst, and the catalyst includes sulfonic acid type imidazolium ionic liquid. The sulfonic acid type imidazolium ionic liquid is a type of acidic functionalized ionic liquid, and has the advantages of both a solid acid and a liquid acid. The sulfonic acid type imidazolium ionic liquid is adopted as an active ingredient of the catalyst, and may remarkably improve a conversion rate of the reaction raw materials and increase a yield of the 2-mercaptobenzothiazole. Meanwhile, due to the characteristics of high catalytic activity, no volatilization, low corrosion, high thermal stability and the like of the 2-mercaptobenzothiazole, the preparation method also has the comprehensive advantages of simple process, low cost, low tar yield, high environment friendliness and the like.