In this paper, we propose the enhanced priority control algorithm that adaptively controls the cell service ratio according to the relative cell occupancy ratio of buffer. The asynchronous transfer mode (ATM) provides the means to support various multimedia services in broadband networks. To support multimedia services, various data traffics of different priorities should be controlled effectively. And also it needs congestion control functions required in the netowrk to carry out the control operation. To accomplish this in a flexible and effective manner, priority classes for the different services ar ecommonly used. The proposed enhanced priority control mechanism have two service calsses of the delay sensitive class and the loss sensitive class. The simulation results show that te proposed control mechanism improves the QoS, the charateristics of cell loss probability and mean cell delay time, by selecting propeor relativ ecell occupancy ratio of buffer and the average arrival rate.