With　the　rapid　development　of　wireless　sensor　technology,　recent　progress　in　wireless　sensor　and　actuator　networks　(WSANs)　with　energy　harvesting　provide　the　possibility　for　various　real-time　applications.　Meanwhile,　extensive　research　activities　are　carried　out　in　the　fields　of　efficient　energy　allocation　and　control　strategy　design.　However,　the　joint　design　considering　physical　plant　control,　energy　harvesting,　and　consumption　is　rarely　concerned　in　existing　works.　In　this　paper,　in　order　to　enhance　system　control　stability　and　promote　quality　of　service　for　the　WSAN　energy　efficiency,　a　novel　three-step　joint　optimization　algorithm　is　proposed　through　control　strategy　and　energy　management　analysis.　First,　the　optimal　sampling　interval　can　be　obtained　based　on　energy　harvesting,　consumption,　and　remaining　conditions.　Then,　the　control　gain　for　each　sampling　interval　is　derived　by　using　a　backward　iteration.　Finally,　the　optimal　control　strategy　is　determined　as　a　linear　function　of　the　current　plant　states　and　previous　control　strategies.　The　application　of　UAV　formation　flight　system　demonstrates　that　better　system　performance　and　control　stability　can　be　achieved　by　the　proposed　joint　optimization　design　for　all　poor,　sufficient,　and　general　energy　harvesting　scenarios.