The present invention discloses a mixed type trace element feed additive, a preparation method and a mixing device. The mixing device comprises a gravity chain grinding hammer, an outer wall of the gravity chain grinding hammer is fixedly provided with a toothed strip, outer walls of both sides of the toothed strip are respectively meshed with a half tooth block, side walls of the half tooth blocks are fixedly provided with shaft rods, outer walls of the shaft rods are fixedly provided with first toothed gears, outer walls of the first toothed gear is meshed with a crawler belt, an inner wallof the crawler belt is meshed with a second toothed gear, an outer wall of the gravity chain grinding hammer is sleeved with a chain grinding groove, a plurality of small holes are all arranged in a side wall of the chain grinding groove, an outer wall of an upper end of the chain grinding groove is provided with a feed adding groove, an inner wall of the feed adding groove is movably provided with a circular plate, an outer wall of the circular plate is provided with a feed inlet, an outer wall of a lower end of the chain grinding groove is provided with a stirring cylinder and an inner cavity of the stirring cylinder sleeves a fixing rod. The device crushes a bulk carrier by gravity to form a fine carrier, so that a trace element additive and the carrier are more uniformly mixed, besides, a feed uniformly falls into the chain grinding groove, and the device improves chain grinding efficiency and mixing efficiency.