Abstract: Task scheduling and resource scheduling are two major aspects concerned with cluster system，while most of the arithmetic only consider one of them.To resolve this problem，an admission control-based QoS-aware dynamic request scheduling arithmetic is proposed in this paper.It introduces the probability Pa which combines self-similar network traffic character and acts as a link to connect the task scheduling and resource scheduling.Pa is an function with two independent variables which are service class and load.With the increase of load，Pa varies non increasingly.For queens with different requirements，the Pa’s varying speed is different so as to dynamically arrange bandwidth for every service class in the different load situations.At the end of this paper，the imitate experiment is conducted to testify it’s rationality.