In　system　design　process,　standby　redundancy　is　a　widely　used　technique　to　improve　system　reliability　and　availability.　Typical　standby　techniques　involve　cold　standby,　hot　standby,　and　warm　standby.　In　this　article,　we　investigate　the　repairable　K-out-of-N　system　with　mixed　standby　strategy　containing　both　warm　and　cold　standby.　In　the　proposed　system,　each　component　can　be　in　failure,　cold,　warm,　and　active　states　and　the　components　are　assumed　to　be　repairable.　The　systems　are　modeled　by　continuous　time　Markov　chain　and　the　system　long-run　availability　is　derived.　Furthermore,　the　optimal　configuration　of　standby　components　in　the　system　is　studied　considering　both　system　availability　and　system　running　cost.　Illustrative　examples　are　presented　to　show　the　applications　of　the　proposed　model.