Cirrus clouds have a great impact on optical signal transmission in quantum communication. According to the cirrus cloud characteristics, the cirrus cloud ice particle distribution model is established, and the extinction properties of cirrus clouds are investigated. In addition, according to the scattering features, the quantitative relationships among the cirrus cloud ice water content, transmission distance, link extinction characteristics, channel capacity, and channel entanglement attenuation are analyzed. The change of teleportation fidelity under the influence of noise is studied and the simulation experiment is conducted. The experimental results show that when the transmission distance is 3 km and the cirrus cloud ice water content (volume mass)is 0.4 g·m ^-3, the corresponding link attenuation, channel capacity and channel entanglement are 0.05 dB·km ^-1, 0.94 dB·km ^-1 and 0.52, respectively. In contrast, they are 0.20 dB·km ^-1, 0.82 dB·km ^-1 and 0.07, respectively, when the cirrus cloud ice water content (volume mass) is 0.1 g·m ^-3. From these experimental results, one can see that the performance of the free-space quantum communication channel changes to different degrees under the influence of cirrus clouds. Therefore, the influence of cirrus clouds should be considered in quantum communication, and various performance parameters should be adjusted according to the change of cirrus clouds in order to ensure the communication quality.