The preference principles of EDCF in 802.11e based on Static-State,AIFS and the Backoff Algorithmare three Mechanisms are elaborated.EDCF guaranteeing to QoS(quality of service)of VoWLAN is confirmed theoretically.The performance of Audio,Video and data is compared through establishing Soft-Terminal simulation model in the IBSS of VoWLAN.The QoS performance parameters(Packet loss rate,Delay,Jitter) were discussed in different traffic loads.Simulation result shows that EDCF can provide the guarantee of QoS for VoWLAN