The　effects　of　Sn　doping　on　thermoelectric　performance　of　Mg3Sb2-based　materials　were　investigated.　First　principle　calculation　results　show　an　increased　density　of　state　near　the　Fermi　level　and　flattened　band　structure　after　Sn　doping,　predicting　that　the　introduction　of　Sn　will　enhance　the　electric　transport　properties　as　an　effective　acceptor　dopant.　The　maximum　ZT　of　Mg3Sb2-xSnx　(0　＜=　x　＜=　0.04)　samples　is　0.42　at　773　K　with　x　=　0.02.　Experiments　demonstrate　that　Sn　doping　can　promote　the　thermoelectric　performance　of　p-type　Mg3Sb2　alloys,　however　the　doping　effect　is　limited　by　the　appearance　of　n-type　Mg2Sn　during　the　preparation　processes.　Consequently,　for　further　enhancing　the　thermoelectric　performance　of　p-type　Mg3Sb2-based　materials,　co-doping　or　composite　method　can　be　introduced　while　select　a　reasonable　Sn　doping　amount.