The invention discloses a method for synthesizing a tetrahydrocarbazoles compound. The method is a green preparation method for synthesizing the tetrahydrocarbazoles compound by using phenylhydrazine hydrochloride or phenylhydrazine and cyclohexanone as raw materials and synthesizing 1,2,3,4-tetrahydrocarbazole in one step through condensation and ring-closing. The method provided by the invention comprises the following steps of: mixing the phenylhydrazine hydrochloride or phenylhydrazine, water and inorganic acid; dripping the cyclohexanone at the temperature in a range of 40-90 DEG C for 0.5-4 hours; and after dripping the cyclohexanone, keeping the heat for 0.5-3.0 hours to obtain the high-content 1,2,3,4-tetrahydrocarbazole. The method for synthesizing the 1,2,3,4-tetrahydrocarbazole is economical, simple and convenient and has the advantages of moderate reaction conditions, high yield and product purity, environmental friendliness and the like.