The invention discloses a preparation method of 1,2-
propane diamine, which comprises the following steps of: adding 1,2-
dichloropropane, water,
liquid ammonia and a catalyst in a high-
pressure reactor, raising the temperature to 160-180 DEG C and the pressure to 8-12MPa, and keeping the conditions for reacting for 4-5h; and sampling for carrying out GC (Gas Chromatograph) detection, completely reacting the 1,2-
dichloropropane, cooling a
reaction system to 20-25 DEG C, discharging excessive
ammonia gas, preparing a mixture using the 1,2-
propane diamine as a main component, and rectifying the 1,2-
propane diamine to obtain a finished product. According to the preparation method, the process steps are greatly simplified,
pollution emission does not exist basically, and the cost is lowered. Excessive
ammonia after the reaction is ended can be recycled, and the preparation process can be completed in one high-
pressure reactor, so that the investment and production efficiency of equipment are greatly reduced. According to the invention, complete reaction can be completed by adopting one catalyst, and low distillates obtained after rectification can be used as raw materials for recycling, so that the selectivity of the 1,2-propane diamine is greatly increased.