The present invention relates to a P2P network system. The P2P network system includes: multiple local overlay networks, each comprising multiple proxy service peers; a global overlay network composed of the proxy service peers of all local overlay networks. The proxy service peer is adapted to respond to the request of the requesting peer, query the local overlay network or global overlay network, and return the address information of the requested peer or the requested proxy service peer to the requesting peer. The present invention also relates to a proxy service peer applicable to the foregoing network system, and a method of peer interworking between P2P overlay networks based on the foregoing system. The present invention relieves the load of the proxy service peer, avoids blindness of the requesting peer in selecting the proxy service peer, and achieves load balance between proxy service peers.