Abstract:N - (2 - ethyl) thiophene methylamine was prepared through polymerization reaction using 2-Thiopheneethylamine and formaldehyde as the raw materials. Then 4,5,6,7-Tetrahydrothieno[3,2,c] pyridine hydrochloride prepared through cyclization reaction in the presence of ethylalcohol and hydrogen chloride. The effect of solvent and acid concentration, reaction time, reaction temperature on the synthesis were studied discussed. The best reaction conditions were that acid is in the 30% absolute ethyl alcohol and hydrogen chloride solution, the reaction solvent is ethanol, reaction time carried out for 3 to 5 hours, the reaction temperature is 50-60℃, the optimized two overall yield of about 87%, the content of HPLC is about 99%.