The power electronic devices are difficult to model due to their switching behavior. Conventional quasi-static models are difficult to reflect the dynamic behavior of the switching adequately. Electro-magnetic transient analysis based on time-domain models can offer improved accuracy, but their nonlinear time-varying nature is impractical to analyze the large power system. A model for single phase inverter on the basis of dynamic phasors is established in order to improve the accuracy of simulation and reduce computation. By comparing the dynamic phasor (DP) model and the detailed time domain electromagnetic transient (EMT) model of single phase inverter, the simulation results show that the DP method could ensure simulation accuracy and reduce computational cost.