A channel merging method for a VOD system, said method comprises the steps of: in response to requests from a plurality of clients for a video program, establishing a root channel (S1) and at least one sub-channel (S11), said root channel (S1) being established according to a request from a client that makes the earliest request, each of said sub-channels (S11) being established in response to a request from a client that makes a later request; and monitoring variation of the number of the clients that are using each of said established channels, and maintaining the channel if the number of the clients using the monitored channel is not zero, and closing the channel if the number of the clients using the monitored channel becomes zero.