The　performance　improvement　of　flat-plate　solar　air　collectors　(FPSACs)　is　vital　for　solar　energy　utilization.　Accordingly,　flat　micro　heat　pipe　arrays　(FMHPAs)　have　been　utilized　in　FPSACs　given　their　excellent　thermal　conductivity　and　suitable　specific　surface　area.　To　investigate　the　impact　of　structural　parameters　of　the　flat-plate　solar　air　collector　with　flat　micro　heat　pipe　arrays　and　optimize　the　performance,　this　study　establishes　a　CFD　3D　model　of　the　collector　with　L-shaped　flat　micro　heat　pipe　arrays.　Fin　height　H,　fin　spacing　L,　glass　thickness　D,　and　air　gap　thickness　S-air　are　selected　as　four　important　structural　parameters　for　numerical　work.　Response　surface　methodology　is　adopted　to　recognize　the　significance　of　each　factor　and　realize　the　prediction　and　optimization　of　the　collector＇s　thermal　efficiency.　Results　show　that　the　thermal　efficiency　can　achieve　a　peak　value　of　52.50%.　An　enhanced　heat　transfer　condition　in　condensation　is　obtained　when　the　optimal　fin　height　and　fin　spacing　are　25　and　4　mm,　respectively.　Improved　thermal　insulation　in　evaporation　is　also　achieved　when　the　optimal　glass　thickness　and　air　gap　thickness　are　3　and　35　mm,　respectively.　The　significance　order　of　the　factors　is　H　＞　L　＞　D　＞　S-air.　The　results　can　serve　as　an　important　reference　for　designing　the　flat-plate　solar　air　collectors.