Abstract: Wireless ultraviolet (UV) communication has the characteristics of high speed and high reliability, which can meet the needs of complex environment. The approximate line of sight (ALOS) communication mode was proposed through the process of helicopter assisted landing, and the ALOS link of wireless UV MIMO system was studied. Meanwhile, the error performance of MIMO system in ALOS link under weak turbulence was calculated, the influence of SNR, transmitting power, transmitting (receiving) elevation angle and communication distance on the BER were calculated and analyzed. When the elevation angle of transmitting (receiving) was less than 35, the BER increased rapidly with the increase of elevation angle, the trend growth of BER was slowing down with the increase of elevation angle when elevation was greater than 35. The result indicates that adopting the MIMO technology with antenna array and multi-detector can reduce BER, suppress the atmospheric turbulence and improve the ability of anti-fading in the wireless ultraviolet ALOS link.