We propose a P2P-based Hybrid ALM (Application- Level Multicast) model, which combines local delivery tree and structured backbone network. Each local peer group elects one coordinator according to ACE (Adaptive Coordinator Election) method and all coordinators from local peer groups build up the structured backbone. This two-tier structure provides good scalability for multicast service. In our hybrid application-level multicast, coordinators are the border of local delivery trees and structured backbone. In local side, coordinators manage local peers and construct delivery trees. We construct delivery trees on demand according to different requirements of applications and targets. In backbone side, coordinators collaborate with each others to implement the best-effort delivery. This includes two functions, one is merging route paths to reduce total hops and content replica and keep load balance over the backbone, and another is exchanging the positions of coordinators to minimize the total delay in the backbone.