It hasattractedattention of the researchers worldwide to establish an equivalent model with high accuracy and simple calculation, which will be used to analysis harmonic of nonlinear load in power system. Norton model is widely used in nonlinear load analysis because it is simple to calculate. However, the interaction between harmonic current and voltage is not considered by the traditional Norton model, which has a large error in the analysis results. Therefore, it is necessary to change its structure in order to improve the accuracy of Norton model.In this paper, the harmonics which has the effects on nonlinear loads are classified, the additional current harmonics are represented by different controlled sources. Then, a modified Norton model is proposed based on the traditional Norton model. Finally, by using the two models under different voltages, the results show that there are 2 orders of magnitude difference in the equivalent impedance value of the traditional Norton model, butthe results of modified Norton model have little change and can be approximately equal. Obviously, the modified Norton model proposed in this paper has higher accuracy and stabilitycompared with the traditional Norton model.