Models for the impact load play an extremely important role in assessing the influence of impact load on power system operation. A practical modeling method is proposed in which the impact load is expressed as a controlled current source based on field data. This method is easy to use and applicable to all kinds of impact load. It is proved by test results that this modeling method is both accurate and effective. The application of the method is implemented in an actual power system. The simulation results show that the operation of the impact load affects the useful life of nearby generator units and the effect of multiple impact loads should be determined by simulating.