Orthogonal frequency division multiplexing based on coherent detection is considered as one of significant solutions for future high-speed optical communication technology. However, because the structure of coherent optical detection system is complex and hard to implement, the subcarrier heterodyne detection technology is utilized to detect the subcarrier orthogonal frequency division multiplexed optical signal. The transmission system of atmospheric turbulence channel is established. The close form expressions for subcarrier average carrier-tonoise ratio (CNR) and average bit error rate (BER) are derived. The effects of opticallocal oscillator power and modulation index on average bit error rate of the system are numerically analyzed and verified by simulation experiment. The results show that subcarrier heterodyne detection is able to further improve the average CNR and therefore to obtain a better BER performance of the system compared to direct detection. When the order of the received optical is microwatts and the optical local oscillator power is close to -11 dBm, the best value of average CNR would be achieved. When the local oscillator power is larger than -11 dBm, the average CNR gradually reduces and the average bit error rate raises with the increase of optical local oscillator power. When the received optical power is larger than - 17 dBm and the average BER is greater than 10- 5, the reliability of wireless optical communication system under weak turbulence would be ensured.