The disclosure provides a downlink transmission method and an eNodeB in a multiple input multiple output system. The method includes: obtaining channel quality indication of a User Equipment (UE) to generate a channel condition indication value; obtaining channel rank indication of the UE to generate a channel correlation indication value; obtaining uplink channel impulse response estimation data of the UE to generate a channel variation state indication value; selecting a downlink transmission mode according to the channel condition indication value, the channel correlation indication value and the channel variation state indication value; transmitting data to the UE in the selected downlink transmission mode. Because of extracting information from a current channel as a basis of a subsequent selection of the downlink mode, the disclosure can greatly improve a resource utilization ratio of a system and realize a better wireless transmission effect.