Accurate planning and design for combat mission is UAV's significant characteristic. Therefore, it is feasible and necessary to evaluate its combat effectiveness predicatively. An evaluation method for UAV penetration and reconnaissance effectiveness based on projection and distance of vague sets was proposed, and the vague value expression of the indexes was offered. On this basis, a mathematical model of UAV penetration and reconnaissance effectiveness evaluation was established by the vague sets projection and distance of multiple attribute fuzzy decision theory and ranking method of mission plans was given. Finally, via an example, the result of this method was correct, which can be a reference to UAV fight decision making.