The invention provides an auxiliary device for heavy iron gate installation. The auxiliary device mainly comprises a planetary gear train labor-saving mechanism, a lever force arm supporting mechanism, an angle fine-adjustment mechanism and a ratchet wheel reversing mechanism. The auxiliary device has the advantages of being capable of solving the problem that it is difficult to install heavy iron gates in rural areas, lowering the operation danger greatly and increasing the safety factor. The auxiliary device needs to be operated manually according to design, and the applicability is improved to the greatest extent on the complex work condition; the planetary gear train and lever labor-saving structures are arranged so that few persons, like one or two persons can complete operation, and the human cost is greatly saved; on the operation condition of many persons, great potential danger caused by emergent accidents can be lowered in the manual installation process.