A non-clipped quadrature phase shift keying (QPSK) sine-like modulation technology is proposed in this paper and applied to the atmospheric laser communication system. The atmospheric laser communication channel model is introduced and the atmospheric laser communication system model of non-clipped QPSK sine-like modulation is given. Based on there, the power efficiency, bit error rate (BER), outage probability and channel capacity of atmospheric laser communication systems which adopt non-clipped QPSK sine-like modulation and direct current bias sub-carrier intensity modulation are compared and analyzed. The results demonstrate that the proposed scheme has better anti-noise performance, higher power utilization, lower outage probability and higher channel capacity, and improves the performance of atmospheric laser communication system. The scheme can satisfy the requirements of atmospheric laser communication system.