In order to realize single mode wireless optical equipment suitable for near ground, a single mode fiber receiving free space optical communication system is designed. A design method of two-level tracking and aperture smoothing is proposed to inhibit the influence of air turbulence and equipment shaking. In this paper, the 900 m field experiment is completed, which reaches the max single mode fiber coupling receiving efficiency of 20% and the received power jitter is less than 6 dB at both ends. The experiment data show that the method of two-level tracking can suppress atmospheric turbulence and shaking. At last, the improvement direction for the future is proposed.