Disclosed is a networked transmission system and method for stream data. The system comprises a network, a streaming server and an ordered series of a first up to n-th cooperative-sharing groups. There is a cooperative relationship among all users' terminals in a cooperative-sharing group. The streaming server provides a plurality of programs with stream data, each program being divided into one or more audio/video clips by a time-slot unit. The streaming server transmits the one or more audio/video clips to the leader node of the first cooperative-sharing groups. The leader node of each cooperative-sharing group transmits the currently received audio/video clip to the users' terminals within the same cooperative-sharing group, and passes the received audio/video clip to the leader node of the next cooperative-sharing group after one time slot.