Aiming at the problem that atmospheric turbulence causes optical signal damage in satellite-to-ground laser communication, we experimentally set up a kind of space laser communication system which can compensate for atmospheric turbulence. The system uses mode diversity reception combined with maximum ratio combining method to compensate for atmospheric turbulence, the coherent detection technique is adopted to detect high-order modulation signals. Transmission experiments are carried out under different turbulence intensities, and the results show that: Compared with a single-mode fiber receiving system, the performance of the mode diversity receiving system has large improvement, with the increase of turbulence intensity, performance improvement is more significant. Under the weak, moderate, and strong turbulence intensities, in the condition of the same target BER, compared with the single-mode fiber receiving system, the mode diversity receiving system reduces the link loss of about 4.2 dB、5.1 dB, and 5.5 dB, respectively. Under the weak, moderate, and strong turbulence intensities, in the same target interruption probability, compared with the single-mode fiber receiving system, the mode diversity receiving system reduces the link loss of about 4.2 dB, 5.1 dB, and 5.5 dB, respectively.