In order to investigate the impact of channel model parameters on the channel capacity of a multipleinput multiple-output (MIMO) system,a novel method is proposed to explore the channel capacity under Rayleigh flat fading with correlated transmit and receive antennas.The optimal transmitting direction which can achieve maximum channel capacity is derived using random matrices theory.In addition,the closed-form expression for the channel capacity of MIMO systems is given by utilizing the properties of Wishart distribution when SNR is high.Computer simulation results show that the channel capacity is maximized when the antenna spacing increases to a certain point,and furthermore,the larger the scattering angle is,the more quickly the channel capacity converges to its maximum.At high SNR (＞12 dB),the estimation of capacity is close to its true value.And,when the same array configuration is adopted both at the transmitter and the receiver,the UCA yields higher channel capacity than ULA.