The IEEE 802.11 MAC layer lacks the limitation of QoS guarantee, and the current research and improvement of IEEE 802.11 differentiated services are mostly based on single rate, and rarely consider the research in the case of multi-rate. Aiming at this situation, this paper analyzes the IEEE 802.11 protocol mechanism in depth., and established a multi-rate IEEE 802.11 protocol model. Based on this, a IEEE 802.11 differentiated service solution is proposed: dynamic timeslot base on probability of channel access (DTPCA). By detecting the network information, the strategy can update the network node-related protocol parameters adaptively in real time, which can effectively realize the multi-rate differentiated service performance and improve the system throughput at the same time. Through theoretical analysis and detailed simulation experiments, the effectiveness of the proposed strategy is confirmed. Moreover, the strategy is easy to control and simple to implement, and it is easy to be applied and promoted in the actual network.