Group key agreement is one of the important means to ensure group secure communication for wireless networks. In 2007, Tseng et al. proposed an efficient group key agreement protocol in wireless mobile environment. In this paper, by analyzing the security of the Tseng's protocol, the authors have found that the Tseng's protocol is not an authenticated protocol and cannot resist active attacks. By improving the Tseng's protocol, the authors propose a new dynamic authenticated group key agreement protocol. Due to using ID-based public key, the expense of building and managing public key infrastructure is decreased, and the protocol supports mutual authentication between nodes. The analysis results show that this protocol can satisfy the security rules of group key, meanwhile, reduce the computation and communication cost of the ordinary nodes.