The embodiment of the invention discloses a method for controlling the number of neighbor nodes of a client, and a device and a cache system thereof, wherein the method comprises the steps of receiving a connection request message sent by the client and used for requesting the establishment of the connection with the neighbor nodes, wherein the connection request message includes data download rate of the client and the number of the neighbor nodes which are connected currently; obtaining the threshold of the number of the neighbor nodes of the client according to the data download rate; and rejecting the connection request of the client when the connecting number of the neighbor nodes which are connected currently of the client is equal to the threshold of the number of the neighbor nodes. The embodiment of the invention can avoid a large amount of unnecessary additional bandwidth consumption due to an excessively large number of the neighbor nodes, and realize the dynamic reasonableadjustment of the number of the neighbor nodes of the P2P client.