In　this　study,　the　GaN　films　have　been　prepared　by　a　green　and　low-cost　plasma　enhanced　chemical　vapor　deposition　(PECVD)method　on　Al2O3　substrate,　along　with　Ga2O3　and　N-2　as　gallium　source　and　nitrogen　sources,　respectively.　The　results　show　that　the　oxygen　content　in　the　GaN　films　is　significantly　influenced　by　the　reaction　temperature　and　N-2　flow　rate.　The　uniform　and　high　crystallinity　GaN　films　were　obtained　at　950　degrees　C　with　N-2　flow　rate　150　sccm,　which　was　also　proved　by　high-　resolution　transmission　electron　microscopy　(HRTEM)　analysis.　It　is　found　that　the　high　energy　nitrogen　plasma　and　additive　graphite　play　vital　role　in　the　growth　of　the　high-quality　GaN　films;　and　the　graphite,　used　as　reductive　agent,　avoided　the　unfavorable　effect　caused　by　the　hydrogen　radicals,　thus,　contributing　to　the　GaN　nucleation.　Moreover,　the　photoresponsivity　of　the　GaN　film　was　observed　to　be　0.0125　A/W　by　365　nm　laser.　Therefore,　the　GaN　nanofilms　prepared　by　the　proposed　green　and　low-cost　PECVD　method　present　a　strong　potential　of　application　in　photoelectric　devices,　such　as　ultraviolet　photodetector,　light　emitting　diodes　and　epitaxial　substrate　for　the　photoelectric　materials.