Abstract: In the prophase of simulation,the main tasks are the data transform and the model reduction.On the basis of the study on data transform,the analysis of the first reduced order method applied in model reduction is given.And the second reduced order method is put forward,which is mainly used in the second order system.By analyzing an example,the utility of this method is proved,furthermore,this method keeps high precision both in low frequency and in high frequency.The results indicate that when the frequency reaches 100 Hz,the relative error is only 1.18%.At the same time,this method keeps some inherent properties of the second order system.