Abstract: In this paper, a single server FIFO queueing system under long-range dependent input traffic in ATM network is studied.Some theoretic results of the cell loss rate in such a system under Gaussian assumption are given.Simulations indicate that queueing analysis is more accurate than some other published results. It is compatible to the short-range dependent traffic.With that method,a unified equation can be used to get the performance of queueing system under input traffic with different autocorrelation structure.