A　field　measurement　campaign　for　ozone　and　ozone　precursors　(VOCs　and　NOx)　was　conducted　in　summer　2011　around　a　petroleum　refinery　in　the　Beijing　rural　region.　Three　observation　sites　were　arranged,　one　at　southwest　of　the　refinery　as　the　background,　and　two　at　northeast　of　the　refinery　as　the　downwind　receptors.　Monitoring　data　revealed　the　presence　of　serious　surface　O-3　pollution　with　the　characteristics　of　high　average　daily　mean　and　maximum　concentrations　(64.0　and　145.4　ppbV　in　no-rain　days,　respectively)　and　multi-peak　diurnal　variation.　For　NOx,　the　average　hourly　concentrations　of　NO2　and　NO　were　in　the　range　of　20.5-46.1　and　1.8-6.4　ppbV,　respectively.　For　VOC　measurement,　a　total　of　51　compounds　were　detected.　Normally,　TVOCs　at　the　background　site　was　only　dozens　of　ppbC,　while　TVOCs　at　the　downwind　sites　reached　several　hundreds　of　ppbC.　By　subtracting　the　VOC　concentrations　at　background,　chemical　profiles　of　VOC　emission　from　the　refinery　were　obtained,　mainly　including　alkanes　(60.0%　+/-　4.3%),　alkenes　(21.1%　+/-　5.5%)　and　aromatics　(18.9%　+/-　3.9%).　Moreover,　some　differences　in　chemical　profiles　for　the　same　measurement　hours　were　observed　between　the　downwind　sites;　the　volume　ratios　of　alkanes　with　low　reactivity　and　those　of　alkenes　with　high　reactivity　respectively　showed　an　increasing　trend　and　a　decreasing　trend.　Finally,　based　on　temporal　and　spatial　variations　of　VOC　mixing　ratios,　their　photochemical　degradations　and　dispersion　degradations　were　estimated　to　be　0.15-0.27　and　0.42-0.62,　respectively,　by　the　photochemical　age　calculation　method,　indicating　stronger　photochemical　reactions　around　the　refinery.