Abstract: Adaptive closed-loop multipleinput multiple output (MIMO) cross-layer scheme is proposed to improve wireless communication network spectral efficiency. The scheme is scheduled through combining adaptive modulation (AM) at physical layer with automatic repeat request protocol (ARQ) at data link layer.By utilizing feedback information, the transmitter updates the modulation mode adaptively, chooses optimal transmitter beam-steering vector and retransmitted data automatically, to form the three-feedback.The paper presents close-form expressions of the spectral efficiencies and the probability of outage under imperfect feedback, and analyzs the effects of delayed feedback on the system performance gains.The simulation results show that compared to single input single output (SISO) cross-layer system and open-loop MIMO cross-layer system, the performance of the adaptive closed-loop MIMO cross-layer system is observably enhanced.