关键词: 带时间状态Pctri网，关键路径，分析，算法

Abstract: Using extended time Petri net, the directional network of project planning was converted into its Petri net model. Any potential limitations were analyzed by the methods of Petri net and corrected firstly. hhe critical path of net was automatically got after operating network for pruning optimization. This algorithm has better effectiveness than the existing methods,and is easy to realize.

Key words: Extended time Petri net, Critical path, Analysis, Algorithm