Along with the dramatic development of wireless network technologies and portable devices, wireless group applications are rapidly innovated to provide online services via wireless broadband networks. This development has led to a prime concern for providing clients with a secure and efficient key management system for group services such as multimedia conferencing, stock quoting and so on. In this paper we propose a new hybrid group key management approach which is suitable for the cellular wireless environment. This new approach has a two-level structure where the group users are sub-divided into clusters, hence reducing the rekeying cost in the key updating. We demonstrate that our proposed approach can achieve better efficiency when compared to the conventional Logical Key Hierarchy scheme.