Direct　chemical　vapor　deposition　of　graphene　on　semiconductors　and　insulators　provides　high　feasibility　for　integration　of　graphene　devices　and　semiconductor　electronics.　However,　the　current　methods　typically　rely　on　high　temperatures　(＞1000　degrees　C),　which　can　damage　the　substrates.　Here,　a　growth　method　for　high-quality　large-area　graphene　at　300　degrees　C　is　introduced.　A　multizone　furnace　with　gradient　temperature　control　was　designed　according　to　a　computational　fluid　dynamics　model.　The　crucial　roles　of　the　chamber　pressure　in　the　film　continuity　and　hydrogen　composition　in　the　graphene　defect　density　at　low　temperature　were　revealed.　As　a　result,　a　uniform　graphene　film　with　the　Raman　ratio　ID/IG　=　0.08　was　obtained.　Furthermore,　a　technique　of　laminating　single-crystal　Cu　foil　as　a　sacrificial　layer　on　the　substrate　was　proposed　to　realize　transfer-free　growth,　and　a　wafer-scale　graphene　transistor　array　was　demonstrated　with　good　performance　consistency,　which　paves　the　way　for　mass　fabrication　of　graphene　devices.