To prove the ability that air defense system deals with multi objects, Threat estimation and sequencing to targets model based on assistant decision making systems is established. At first, simple states theory and concept, then introduces threat estimation and sequencing model based on assistant decision making systems, establishes knowledge base and analyses the threat factor of air target. The model has man-machine alternating function and self-learning function, it can obtain or modify the knowledge automatically and can intelligently ascertain the threat degree of targets. The model can offer the effective decision tool for commander to carry on operational command.