With the development of the air platform,the application demand of wi reless optical communication in the slant path is gradually increasing,but the atmospheric effect still has a great impact on the performance of the current ne ar infrared ground-air slant path wireless optical communication system.In ord e r to solve this problem,this paper proposes to use far infrared as the working wavelength of the ground-air slant path wireless optical communication system. B ased on the physical model and weak fluctuation theory,the transmission loss,s cintillation index and bit error rate (BER) of the far i nfrared system in the up link and downlink are studied,and the factors that affect the performance of the far infrared wireless laser communication system,such as zenith angle,atmosph eric visibility,transmission distance and system signal-to-noise ratio (SNR),ar e analyzed by numerical simulation.The results show that in the ground-air sla n t path wireless optical communication link,far infrared has obvious transmissio n advantages under severe weather with low visibility,and it has strong anti-t u rbulence ability in long-distance transmission with a zenith angle greater than 30°;In the on-off keying (OOK) modulation mode,the far infrared ground-air s la nt path wireless optical communication system BER decreases rapidly with the increase of the system SNR.