Introduction  Load， as the part that ultimately consumes active power， has a very important impact on the stability of the system. Therefore， the influence of different load models on out-of-step oscillation characteristics of power system is studied in this paper.

  Method  This paper took a large grid’s regional discontinuity as the research target to comprehensively analyze the effects of different load models on the oscillation center and action of out of step splitting device using BPA program developed by China Electric Power Research Institute.

  Result  The simulation results show when using the ZIP static load model， the line Ucos curve demonstrates the best periodic integrity ， as the proportion of induction motor type load increases， the Ucos curve’s periodic integrity becomes worse， it even leads to a subversive change in the conclusion whether the out of step splitting device can react. In addition， different load models also cause the oscillation center migration.

  Conclusion  Therefore， the credibility of simulation results can only be guaranteed by using the most realistic load model.