The invention relates to a fast preparation method of ferrous microporous composite molecular sieves. According to the method, firstly, single molecular sieves are prepared in a reaction kettle, then, ferric nitrate is doped, heating and crystallization are carried out in a heating furnace, high-temperature roasting is carried out in a rotating furnace, ferrous microporous composite molecular sieve powder products are fast prepared, and the prepared ferrous microporous composite molecular sieve powder body particles are dispersive-molecule crystals containing 10-membered rings and 12-membered rings, the diameter of the powder particles is 2 to 5mum, the powder particles can be matched with various chemical substances to be used as catalysts, and the method provided by the invention belongs to a very ideal method for fast preparing the ferrous microporous composite molecular sieves.