Dynamic peer communication is the most complicated of all the group communication mode. The paper concisely analysed five typical group key agreement protocols put forward in recent years, they are: centralized key distribution (CKD), burmester-desmedt (BD), steer et al. (STR), group diffie-hellman (GDH) and tree-based group diffie-hellman (TGDH). A new group key agreement protocol (TTS) is proposed and compared with other protocols. This protocol has the advantage in computation, and fit to common network condition.