The invention relates to a preheating device for a siderite magnetizing and calcinating rotary kiln and a method for preheating lump ore. The reheating device is an equilateral polygon vertical preheating device, and the preheating device comprises a feed port, a storage warehouse, a discharge pipe, a preheating chamber, a push rod device, a discharge chute, a smoke outlet and a smoke circular pipe. The invention further provides a siderite magnetizing and calcinating rotary kiln comprising the preheating device. In addition, the invention further provides a method for preheating lump ore based on the siderite magnetizing and calcinating rotary kiln. According to the invention, the preheating device can effectively improve the heat transfer efficiency of the whole device, reduce the length dimension of the rotary kiln, reduce the covering area of the kiln body, reduce the heat consumption and the power consumption of the working procedures, reduce the difficulty of production operations and improve the production operation efficiency.