Abstract: Based on the model of high altitude platforms position instability, the symbol error probability of PPM on inter-platforms optical links was derived. Based on the symbol error probability, the effect of three moving modes due to high altitude platforms position instability on the performance of inter-platforms was analyzed. The simulation results show that platforms rotation has the greatest influence on inter-platforms optical links, and the changing of inter-platforms distance has the lowest influence on inter-platforms optical links. A wide optical beam waist has better adaptability in platform instability. But when beam waist is more than 20 rad, the improvement of system performance is insignificant.