In this paper,we study the performance of RED (Random Early Detection) algorithm implemented in ATM switches.The throughput,fairness and delay of RED algorithm are studied in the environment of homogeneous and heterogeneous traffic and in the environment of time-varying available bandwidth.It show that RED algorithm,which should be integrated with EPD algorithm,reduces the average queuing delay through effectively controlling the average queue length.Through performance comparison with other packet discard schemes,the ATM switch with RED+EPD algorithm can provide higher throughput,better fairness and smaller delay than the switch with EPD algorithm,so it can support the traffic with delay requirement.