This paper aims to research the legal issues regarding to Unmanned Aerial Vehicles (UAVs) in the light of Law of Armed Conflict. This article at first investigates use of UAVs in the context of legality or illegality in all circumstances or some circumstances. Then, it surveys Distinguish Principle and its rules on UAVs. In general, evaluation of International Law and States Practice show that the use of UAVs in the war is not Impeded. UAVs are not weapons, so arms control regime cannot applied to them. As the most important result, in the context of Law of Armed Conflict, these Vehicles considered as means. The use of UAVs should be based on the “Distinguish Principle”. In result, every verdict on legality or illegality the use of UAVs depends on status and characteristics of UAVs.