Reliability　is　an　important　metric　for　unmanned　aerial　vehicles　(UAVs)　to　perform　important,　complex,　and　dangerous　tasks.　In　addition,　reliability　influences　the　operational　cost　in　UAVs　routing.　In　order　to　reduce　the　operational　cost　of　UAVs　tasks,　a　method　of　routing　strategy　optimization　is　proposed　from　a　view　of　mission　reliability　in　this　paper　to　address　the　limitations　in　routing　scheduling.　Different　from　previous　studies　on　the　UAVs　routing　optimization　problem,　this　paper　proposes　a　method　that　can　reduce　the　operational　costs　of　UAVs　tasks　based　on　the　mission　reliability.　This　method　includes　two　stages:　the　pre-optimization　stage　and　the　rescheduling　stage.　In　the　pre-optimization　stage,　an　optimal　UAVs　route　solution　is　obtained　for　all　the　targets,　while　in　the　rescheduling　stage,　new　UAVs　are　dispatched　to　the　unvisited　targets　in　the　pre-optimization　stage　based　on　the　new　optimal　UAVs　route.