Based on the premises of transparent posture and dynamic mission environment, the mathematical modeling of the single Unmanned Aerial Vehicle (UAV) online path planning problem is carried out. Then, Receding Horizon Control method (RHC) and 2D-equal-step path generation methods are briefly introduced, which are combined with the Improved Wolf Pack Algorithm (IWPA) to solve the single UAV online path planning problem modeled in the previous. The simulation results show that the new algorithm can be used to solve the single UAV online path planning problem aiming at moving targets in dynamic mission environment, and the performance of the improved wolf pack algorithm is more powerful than the original wolf pack algorithm in this process of application.