Abstract: Network planning can be used to show many difficult problems intuitively in project management, which helps to analyze and solve them. But it also has obvious defects, for example, (1) direction character with no loop of an activity network illuminates that dynamic programming is capable to it, but non-phases of an activity network in generally makes the algorithm cannot be used directly; (2) an activity network which created arbitrarily may be intricate easily in presentation, which leads difficulty to study; (3) the problem of representing activity-on-arc representation network with the least dummy activities is NP-hard, therefore many different activity networks may be created for an activity system, which blocks study on scheduling and planning management, etc. It will help to resolve above problems if transforming an activity network into an equivalent multi-phases network that each activity lies in a corresponding phase. Creating an equivalent multi-phases activity network need to add dummy activities. In this article, we design a method to create the equivalent multi-phases network by adding the least dummy activities to an activity network, which helps to found a more appropriate representation of activity network.

Key words: multi-phases activity network, improved Ford-Fulkerson algorithm, network planning