Abstract: Soft simulation replicated the flight performence of coaxal pilotless helicopter controlled by classical navigation algorithm based on d(deviation distance) and its- variation ratio d · in various situations (undisturbed, constant gust disturbed). The heading bias, sideslip velocity and deviation distance were analyzed to explain the phenomenon of sideslip in the situation of constant gust disturbance during the course flight when using the classical algorithm. To solve this problem an amendatory algorithm was proposed and analyzed with simulation. Two approaches were compared to analysis the effect of introducing different feed-back (one was only using heading feed-back, the other was using heading feed back and integral of d). The results indicate that the algorithm based on heading feed-back and integral of d performs well in smooth turning and achieves better performance in avoiding sideslip on the premise of achieving satisfying navigation precision. As a result, the amendatory algorithm proposed improves the course flight efficiency of coaxal pilotless helicopter.