Abstract: Because the study and assessment on impact of the electric arc furnace on the grid system is an important analysis work of power quality, a more accurate model is built to analyze power quality for a certain type of electric arc furnace. Based on the differential equations of deterministic dynamic arc model and a certain type of electric arc furnace testing voltage and current data, by choosing simulation period that the power quality influences the power grid seriously, the simulation system can well reflect the harmonic current, flicker, voltage fluctuation and three phase unbalance degree of a certain type arc furnace during the melting period, which reaches ideal simulation results of power quality impact.