MIMO system communication method and apparatus under time division duplex mode

The invention relates to the field of wireless communications, which discloses a communication method and a device of a multiple input multiple output system under TDD mode, and makes the MIMO system be improved under the TDD mode. During the invention, a first device calculates pseudo-characteristic beam-forming vector used by first layer data and calculates M-1 candidate beam-forming vectors orthogonal with the pseudo-characteristic beam-forming vector according to channel parameters corresponding to a transmitting antenna of a second device; and the first device selects K beam-forming vectors having good performance from the M-1 candidate beam-forming vectors as the beam-forming vectors used from the second layer data to the K+1(th) layer data according to the feedback of the second device.