We present an analysis of the impact of afluctuating-loss channel on free-space quantum key distribution (QKD). Considering the characteristics of the fluctuating-loss channel, a scintillation discriminator that acts according to the information of instant channel loss is proposed to help improve the performance of a free-space QKD system, which suffers from the influence of atmospheric turbulence. Theoretical and numerical results show that this discriminator is a useful tool for increasing se
