The invention discloses a method for preparing acid dye raw powder from a CLT acid isomer mixture. The method is mainly characterized in that byproducts generated in the production process of an organic dye intermediate of CLT acid and H acid or byproducts generated in the H acid production process are used; diazo reaction is performed under a certain reaction condition; coupling reaction is performed; and the acid dye raw powder, i.e., acid purple raw powder/acid rose red raw powder is obtained. The cheap and fine acid dye used for nylon dying can be prepared; and the pollution possibly caused on the environment due to byproducts generated in the intermediate production process is reduced, so that the comprehensive and sustainable development of the industrial production is achieved.