It is important for distributed multimedia applications to assure end-to-end QoS of media streams. Moreover, the end-to-end QoS needs to be managed adaptively according to fluctuation of system states and variation of user requests. In this paper, a model of adaptive QoS management platform for distributed multimedia applications is proposed. In this model, the adaptive QoS management is achieved by direct and indirect cooperation of layered multi-agents. By using the layered multi-agents system, the proposed QoS management platform can flexibly adapt to user's QoS requirements and large variation of system states, and can quickly adapt to small fluctuation of system states, simultaneously.