Tetrahydro-carbazole was synthesized by cyclization reaction of phenyl-hydrazine and cyclo-hexanone with the yield of 70.5%. And 9-ethyl tetrahydro-carbazole was synthesized by alkylation of tetrahydro-carbazole with ethyl bromide. The structures of product were characterized by 1HNMR和13CNMR. The optimum reaction conditions for synthesis of 9-ethyl tetrahydro- carbazole were as follows: n(tetrahydro-carbazole) : n(ethyl bromide) : n(sodium hydroxide)=1:4:1.5, m(tetra- hydro-carbazole) : m(potassium iodide)=1:0.01, c(hexadecyl trimethyl ammonium bromide)=2.5×10-3 mol/L, c(tetrahydro-carbazole) =0.50 mol/L. The yield of 9-ethyl tetrahydro-carbazole was 86.0% under the optimum conditions in the solvent of acetonitrile for 9 h. Compared with the traditional process (chlorination of cyclohexanone with chlorine, followed by condensation）, the synthesis could avoid the formation of chlorinated by-products and is easily to be commercialized.