Based on the investigation of harmonic generation reason of the main equipment and its harmonic characteristics in the steelmaking line, the power system of an iron and steel enterprise is modeled by ETAP software. The propagation characteristics in the power grid is studied and the harmonic pollution responsibility of the iron and steel enterprises in the PCC is clear. The possible resonant points are found out via simulation and calculation and the resonant causes are analyzed and verified. Finally, the filter is designed according to parallel resonance in system. It provides a method for harmonic and resonance suppression and power quality improvement of enterprise power grid. This work is supported by National Science and Technology Support Program of China (No. 2015BAA01B04).