MAC(Medium Access Control) is demanded to provide end-to-end QoS(Quality of Service) for a variety of traffic in the wireless networks. When all the traffic is integrated in the channel, the main difficulty of the MAC protocol is how to efficiently support multi-class traffic in the limited bandwidth wireless channel. In this paper, we proposed the dynamic bandwidth slot method for improving QoS of the real time traffics. In this paper, we used in-band scheme to send dynamic parameter and considering buffer size and delay variation, we enabled 2 state bits to send to base station in mobile station. The proposed algorithm is to guarantee QoS of real time traffic and maximize transfer efficiency in wireless networks.