Abstract: The surface of metal magnetic powders was modified by polystyrene, which was formed by chemical bond quomodo grafting styrene to the surface of metal magnetic powders by silane coupling agent A-151.We research the temperature, dosage of silane coupling agent A-151, dosage of BPO, and length to the graft efficiency. The appearance, phase constitution were characterized by SEM, RA-IR. And the powders were randomly dispersed in paraffin for microwave electromagnetic parameters test and comparison. The results show that a high resistivity film was formed on the powders surface by chemical bonding, and the real and imaginary parts of complex permittivity of the sample decrease largely but corresponding complex permeability decrease slightly.