Abstract：Polymer coated Fe3O4 magnetic nano particles are selected as a magnetic seeding for superconducting magnetic separation to expand its scope of application in the wastewater treatment. Fe3O4 nano particles are synthesized at the room temperature, and the properties of nano materials are determined by X-ray Photoelectron Spectroscopy(XPS), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM). It is shown that the diameter of nano particles ranges from 6~8nm, the surface of Fe3O4 nano particles is overlaid with the polymeric chain with carboxyl, and the nano particles show super paramagnetic properties at the room temperature. The decontamination capacity of the wastewater is tested using the dyeing wastewater. Quality indicators, such as the turbidity and Chemical Oxygen Demand (COD) are measured before and after the treatment with polymer coated Fe3O4 nano particles and compared. It is shown that the magnetic nano particles can effectively purify the waste in the dyeing wastewater.