First-principles　computations　were　performed　to　investigate　the　performance　of　KTiOPO4　(KTP)　as　a　cathode　material　for　potassium-ion　batteries　(PIBs),　including　the　stability　and　electronic　properties　of　depotassiated　structures　and　mechanisms　of　K　deintercalation　and　diffusion.　As　depotassiation　proceeds,　oxygen　hole　polarons　are　produced,　and　there　are　not　peroxides　or　superoxides　formed　after　deep　depotassiation.　The　anionic　oxygen　redox　in　KTP　provides　a　voltage　vs　K/K+　over　4　V　by　the　PBE+　U　method　and　over　5　V　with　the　more　reliable　HSE06　hybrid　functional.　When　all　K　in　KTP　is　removed,　the　calculated　volume　compression　is　only　1.528%.　The　AIMD　simulations　at　300　K　for　TiOPO4　verify　its　thermal　stability.　The　PBE+U　calculations　predict　a　low　ion　diffusion　barrier　of　0.29　eV　in　bulk　KTP,　indicating　a　good　charge-discharge　rate　for　KTP　as　a　cathode　for　PIBs.　All　of　the　calculated　results　indicate　that　KTP　can　be　a　promising　cathode　material　for　PIBs.