The invention discloses a self-adaptive beam selection and transmission method in the relative MIMO system. In the method, according to the second order characteristics statistical of the signal channel in the relative MIMO system, a receiver determines to send beam set and feed backs it to an inchoation. At each moment of transmission, according to current signal channel characteristics, the receiver chooses some beams form the beam set as sending beam which is used at present, at the same time, determines the power and bit allocation of each beam, and feedbacks the result to a sender. According to the result feed backed by the receiver, the sender chooses the corresponding beam from the sending beam set, and carries out the corresponding power and bit allocation, and then sends out. In the method, self-adaptive transmission method which is based on the beam selection, beam power and bit allocation is used, and multiplexing signal correlation is removed, at the same time, the transmission performance of MIMO system is improved.