Influences　of　biomass　burning　(BB)　on　a　high　altitude　site　were　investigated　by　collecting　fine　particulate　matter　(PM2.5)　samples　from　29　March　to　27　April　of　2012　at　Mt.　Yulong　(4500　m　above　sea　level),　and　analyzing　them　for　selected　chemical　species　including　water　soluble　ions　(WSIs),　organic　carbon　(OC),　elemental　carbon　(EC),　polycyclic　aromatic　hydrocarbons　(PAHs)　and　n-alkanes.　The　mean　PM2.5　mass　loading　for　the　study　was　6.30　+/-　4.90　pg　m(-3),　and　15.48　+/-　2.82　pg　m(-3)　and　1.75　+/-　0.41　mu　gm(-3)　for　a　high　and　a　low　PM　episode,　respectively.　WSIs　accounted　for　62%　of　the　total　mass,　and　SO42-　was　the　dominant　anion　and　NH4+　was　the　main　cation.　PAHs　were　mainly　3　ring　compounds,　fluorene　(Flo)　and　phenanthrene　(Phe)　together　accounted　for　54%　of　the　total　PAHs.　For　n-alkanes,　n-Nonacosane　(C-29)　concentration　was　the　highest　with　the　value　of　1.09　+/-　1.18　ng　m(-3),　following　is　n-Hentriacontane　(C-31)　and　n-Heptacosane　(C-27)　suggested　that　n-alkane　in　our　samples　were　mainly　contributed　by　biogenic　sources.　BB　emission　was　confirmed　by　the　diagnostic　ratios,　and　it　also　had　a　significant　influence　on　aerosol　optical　depth　(AOD)　distribution　and　enhances　the　concentration　of　most　species,　especially　for　OC,　K+　and　EC.　Significant　relationships　were　found　between　daily　fire　counts　and　BB　species,　and　correlation　coefficients　(r)　for　mass,　K+,　OC,　and　EC　were　0.58,　0.57,　0.53　and　0.60　(n　=　29,　P　＜　0.01),　respectively.　It　indicated　that　daily　fire　counts　can　advance　our　understanding　of　how　biomass　burning　affect　aerosols　and　air　quality　at　a　high-altitude　site.