Flexible　perovskite　solar　cells　(F-PSCs)　are　attracting　tremendous　research　interest　due　to　their　light　weight　and　flexibility.　However,　the　poor　quality　of　perovskite　films　caused　by　deformation　of　flexible　substrates　during　a　general　heat　treatment　process　hinders　the　fabrication　of　high　efficiency　flexible　cells.　Here,　a　simple　gradient　heat　treatment　(GHT)　process　is　developed　to　effectively　improve　the　crystal　quality　of　perovskite　films　and　the　efficiency　of　F-PSCs.　The　results　show　that　a　smaller　temperature　fall-off　gradient　will　be　beneficial　to　the　further　growth　of　perovskite　films,　which　helps　to　further　enhance　the　crystalline　quality.　Compared　with　the　conventional　method,　the　power　conversion　efficiency　(PCE)　of　F-PSCs　fabricated　by　a　GHT　process　with　a　relatively　small　gradient　significantly　improved　by　31%,　and　the　maximum　PCE　increased　to　17.37%.　This　work　provides　a　new　idea　for　ameliorating　the　quality　of　perovskite　films　and　enhancing　the　performances　of　F-PSCs.