Wireless ultraviolet communication system is vulnerable to atmospheric scattering and other factors, resulting in low accuracy of communication channel capacity estimation. To this end, a channel capacity estimation method for wireless ultraviolet multiple-input multiple-output (MIMO) communication system is proposed. According to the channel characteristics, the channel capacity estimation model of the wireless ultraviolet MIMO communication system is constructed, the single scattering transmission characteristics of wireless ultraviolet light, the space time coding is improved by using the symbol complement method, and the received energy consumption of the symbols in the advanced detector is set, so that each symbol is kept within the standard power value range, and the channel detection coding of the communication system is completed. The path loss ratio of wireless UV communication is calculated according to different transmission and reception angles, and the final channel capacity of the communication system is estimated by Poisson random distribution. The experimental results show that the transmission rate of the proposed method can be as high as 8 Mbps, the bit error rate is always less than 10-3 bit/s, the estimation accuracy is more than 90%, the estimation time is less than 4 ms, and the estimation effect is good, which can provide a theoretical basis for the development of the communication industry.