To accurately evaluate the jamming effect on terminal guidance radar under active jamming,according to the working process of terminal guidance radar and the characteristic of counteractive active jamming,the ratio of detecting-target-time and the ratio of tracing-error were adopted as indexes,and the relationship between indexes and influence factors and the evaluation methods were analyzed briefly.The indexes were treated by unitary quantification and weighted summation to get the synthetic results.The simulation results show that the evaluation indexes are scientific and easy to be measured,and the evaluation method is simple and effective.