Abstract: Speculative execution is a good way to improve the performance of a superscalar processor.In order to analyze the performance of a speculatively executed superscalar processor,an analytical model is proposed.Being composed of the structural hazard model and data control hazard model,this model can be realized easily.This model is used to study the performance of nine benchmarks.The results prove that deeply speculative execution is very important for a superscalar processor to reach high performance.