We propose to investigate the performance of a satellite-to-ground quantum key distribution (QKD) system that uses key retransmission as a method for improving the system reliability. We develop analytical frameworks based on two three-dimensional Markov chain models allowing us to comprehensively analyze the proposed system’s performance in terms of key loss rate, link utilization, and delay outage rate. Our performance analysis takes into account the physical layer impairments induced by free-space optical channel and receiver noise. Numerical results quantitatively demonstrate that the performance of satellite-to-ground QKD system is significantly improved due to key retransmission. In addition, the appropriate selection of system parameters corresponding to different turbulence conditions to achieve the best performance improvement is also provided.