If the propeller auto rotates after one of engines on turboprop aircraft failed, the auto-rotate propeller will produce negative pulling force, which will endanger flight safety. Firstly，this article introduces the propeller auto-rotate states, negative pulling force mechanism, and changes law according to air speed， then analyzes the influences of slipstream on lifts and drags according to states of propellers, and apply the propeller load coefficient to calculate the difference in lift resistance and lateral heading moment between the two wings, in order to solve the problem of insufficient aerodynamic data in this state. Based on all above, the full state hydrodynamics were established. The dynamic states of airplane were simulated and calculated according to actual control surfaces inputs, and compared to actual flight data. Finally, it was discussed and analyzed that the main factors influencing flight safety due to this special situation were obtained, which are decreases of lateral directional moments and aileron efficiency caused by errors between lifts and drags on different wings. The conclusions are worth of reference to guarantee flight safety, both for turboprop aircraft design to avoid the situation and managing the situation in flight.