Group awareness is the basis of the group cooperation. Its model and application is an important research field in CSCW community. A role based hierarchical group awareness model (RHGAM) on the basis of the previous research is presented in this paper. Regarding role as the basis of the group cooperation, firstly RHGAM constructs a group cooperation environment (GCE), and then GCE is extended by group awareness content, awareness hierarchy, the task decomposition rule. The model divides the awareness information into four levels by decomposition and recombination using a role-task graph and the thinking of group structure. The implementation mechanism of the model to provide group cooperation and awareness mechanism in the project Personal Research Information Workspace is also discussed in this paper.