This paper proposes a collision detection scheme in asynchronous multiuser-multiple input multiple-output (MU-MIMO) transmission and self-interference cancellation. We assume that asynchronous MU-MIMO which realizes the efficient transmission and other antennas can receive preamble signals while the transmission is employed with antennas which are used in asynchronous MU-MIMO. The self-interference can be cancelled by subtracting the short preamble signal which is multiplied by the estimated channel response using the received signal after FFT processing. The effectiveness of proposed method is shown by computer simulation. In addition, interfering power from the interfering user terminal (IT) at the access point (AP) and desired user terminal (DT) is verified in an actual indoor environment.