Magnetic nanomaterials are widely used in biosynthesis, catalysis, as electronic and microwave-absorbing materials, and in environmental treatment because of their high specific surface area, strong magnetism, chemical stability, and good biocompatibility. The chemical coprecipitation method is widely used for the preparation of magnetic nanomaterials due to its simplicity, low cost, and easily-controlled operating conditions. The magnetic nanomaterials prepared by the chemical coprecipitation method are summarized according to the different compositions, including the basic preparation principles, and the factors affecting their morphology, size, and microstructure. The mechanisms of preparing magnetic nanomaterials by chemical precipitation and the process control factors are emphasized. Finally, the preparation of magnetic nanomaterials by chemical coprecipitation is summarized and prospected.