With industry expanding and new technologies booming, more and more, IS Department use team approach to increase their competitiveness and to reach their targets. Project is a special formation with clear mission, target and timeline. Within nine major knowledge territories of Project Management, communication management is the most time consuming for Project Managers. Besides, Projects rely heavily on team members' cooperation to proceed; thus, how to provide a good and effective communication channel is a major factor for successful projects. This research use Jürgen Habermas's Theory of Communicative Action as main approch thourgh out Project Management and Communication Management. The main purpose of this research is to: 1: Finding Project's validity basis thematize and the mode of communication. 2: Finding the rational communication method, which allows both parties to identify themselves toward the goal, and increases the success of Project Manager's leading effort. This research showed the Project Manager use communication management to thematize the truth claim to gain the trust of team members to move along with the project. And also Project Manager will use communication management to emphasize the truthfulness claim of him or herself to get them heard. This will gain the recognition from team members to get the project to reach its goal. Moreover, this research also use the basic conversation for action to find the successfully communication method in IS project and to provide the Project Managers ways to establish effective communication methods.