To improve the safety of UAV operating in airspace, TOPAZ method is introduced for the safety assessment of UAV flight conflict resolution technology. Firstly, the conflict scenes including $45^{\circ}, 90^{\circ}$ crossing encounter for single-aircraft and simultaneous crossing encounter for double-aircraft are added to construct the airspace operation environment for UAV. Then a typical UAV conflict resolution algorithm (a modified GA algorithm) is selected as the safety assessment object and is systematically evaluated according to the process of TOPAZ. Finally, a dynamic heuristic factor is introduced to modify the selected algorithm and validate the improvement of safety level of the algorithm by TOPAZ.
