The invention provides a selection method of cooperative nodes in a peer-to-peer network P2P system, wherein, nodes select the cooperative nodes according to self-service capability, and perform self-adaptive adjustment on the self position in the system to finally form a layered distribution structure. The method comprises the following steps: firstly, the nodes periodically monitor the self-service capability and evaluate a service capability level; and then the nodes select the cooperative nodes according to the self-service capability to perform self-adaptive adjustment on the self position in the system, and data is transferred from a data server to the nodes in the system along the layered structure. The method can help distribute the data to all the nodes in the system as soon as possible, thus reducing system transmission delay and strengthening collaboration of the nodes.