The paper studies the signal detection problem of the smart antennas-MIMO (SA-MIMO) system, which combines MIMO and smart antennas by replacing each antenna of MIMO with a smart antenna array under single-user scenario. First, the system model and related detection algorithms are briefly introduced. Then the paper presents a suboptimal detection theme. The detection theme contains two steps, one is determination of beam-forming vectors by maximum diagonal element (MDE) rule that can reduce the channel correlation among the MIMO channel links, and the other combines ordering successive interference cancellation (OSIC) based the posteriori signal-to-interference-plus-noise ratio (SINR) with the minimum mean square error (MMSE) for achieving further gain. Some numerical results show that the proposed method is viable.