GaN:　Mg　films　have　been　grown　on　sapphire　at　low　temperature　by　metal-organic　chemical　vapor　deposition,　the　properties　of　different　source　flux　GaN:　Mg　materials　were　studied.　When　the　molar　ratio　of　CP2Mg　and　TMGa　is　between　1.4　x　10(-3)　and　2.5　x　10(-3),　the　quality　of　crystal　was　improved　with　the　increasing　molar　ration,　and　the　hole　concentration　was　increased　linearly.　When　the　molar　ratio　is　2.5　x　10(-3)　the　concentration　is　equal　to　that　of　the　film　grown　at　higher　temperature,　and　the　surface　morphology　is　more　coarser.　Taking　the　p-GaN　layer　with　molar　ratio　of　CP2Mg　and　TMGa　of　2.5　x　10(-3)　as　the　light-emitting　diode,　when　the　inject　current　is　20　mA,　the　output　light　power　was　increased　by　17.2%.