The emerging peer-to-peer (P2P) model has recently gained a significant attention due to its high potential of sharing various resources among networked users. Super-peer unstructured P2P systems have been found very effective by dividing the peers into two layers, super-layer and leaf-layer, in which message flooding is only conducted among super-layer. However, current super-peer systems do not employ any effective layer management schemes, which means the transient and low-capacity peers are allowed to act as super-peers. Moreover, the lack of an appropriate size ratio maintenance mechanism on super-layer to leaf-layer makes the system?s search performance far from being optimal. We propose a Dynamic Layer Management algorithm, DLM, which can maintain the optimal layer size ratio, and adaptively adjust peers between super-layer and leaf-layer. DLM is completely distributed in the sense that each peer decides to be a super-peer or a leaf peer independently without the global knowledge. DLM could effectively help a super-peer P2P system maintain the optimal layer size ratio, and designate peers with relatively long lifetime and large capacities as super-peers, and the peers with short lifetime and low capacities as leaf-peers under highly dynamic network situations. We demonstrate that the quality of a super-peer system is significantly improved under DLM scheme by comprehensive simulations.