In this paper,the bit error rate performance of UAV all optical relay laser communication system under atmospheric turbulence channel is studied.In order to reduce the influence of atmospheric turbulence,improve the bit error rate performance of the system,and realize the long distance data transmission,a two hop relay mode based on a combination of Erbium Droped Fiber Amplifier(EDFA)and optical hard limiter(OHL)is adopted for UAV platform with both high altitude horizontal transmission and single input multiple output(SIMO)technology for ramped transmission.Besides,based on a normal distribution and double gamma turbulence model,the effects of pointing error,relay distance,zenith angle,beam scatter angleand platform height on BER performance are analyzed.Simulation results show that UAV OAF system can effectively improve the BER error rate performance of data transmission over long distance.When the transmitting power =19dBm,threshold power =-31 dBm,N=3,the optimal divergence angle is 0.8～1.2 mrad,and zenith angle is controlled within 45°,10 -6 system BER performance can be obtained in 6km relay system.