Abstract: This paper proposes a scheme of network coding for asymmetric data transmission in three-point cooperative communication system. Since the joint using both cooperative diversity and network coding, the diversity gain and coding gain are achieved in wireless communications transmission system. In this paper, the differences of wireless communication environment are fully considered. The scheme with asymmetric modulation ensures the reliability of communication in the poor environment. Meanwhile, it transmits more data in better links to make full use of system resource. The main idea to realize network coding of asymmetric data transmission is to add prior known information in the relay. The prior known information can enhance the coding performance of the system. Simulations show that the proposed transmission scheme can achieve the diversity gain and reduce the BER compared to non-cooperative transmission system. In addition, it can improve the transmission capacity of the communication system.