This　paper　focused　on　VOCs　and　their　source　apportionment　in　urban　Beijing.　Our　monitoring　measured　52　VOCs　in　July　2014　and　January　2015.　The　concentration　of　VOCs　was　in　the　range　of　14.595.2　ppb　in　July　and　2.193.1　ppb　in　January,　with　the　top　five　compounds　of　toluene　(10.7%),　ethane　(6.9%),　ethylene　(6.3%),　n-butane　(5.7%),　and　propane　(5.6%)　in　July　and　ethylene　(14.7%),　n-butane　(14.2%),　ethane　(9.6%),　propylene　(8.0%),　toluene　(7.9%),　and　benzene　(6.9%)　in　January.　The　ratio　of　VOCs　to　CO　reached　0.059　in　July　and　0.022　in　January　on　average.　These　differences　implied　a　potential　seasonal　difference　in　the　VOC　source　contribution.　Then,　we　conducted　a　source　apportionment　study　based　on　21　major　VOCs　and　CO　by　using　probabilistic　matrix　factorization　(PMF)　receptor　model.　According　to　the　similarity　between　the　PMF　analysis　profiles　and　the　known　source　profiles,　combustion　sources,　petrochemical　industry　sources,　solvent　utilization　sources,　and　gasoline　evaporation　sources　were　identified.　The　correlation　coefficient　(R)　between　the　PMF　analysis　profile　and　the　source　profile　reached　0.680.87　in　July　and　0.530.92　in　January.　The　better　apportionment　performance　in　July　was　mainly　due　to　the　use　of　intensive　VOC　observations　at　a　3-h　resolution.　When　we　conducted　another　PMF　source　apportionment　for　July　based　on　12-h　resolved　concentration　input,　the　R　values　decreased　to　0.470.73.　Thus,　the　PMF　model　depends　heavily　on　the　sample　number　of　concentration　inputs,　and　intensive　observation　is　more　propitious.　Our　PMF　apportionment　results　showed　that　combustion　sources,　petrochemical　industry,　solvent　utilization,　gasoline　evaporation,　and　other　sources　contributed　ambient　VOCs　in　Beijing　urban　areas　of　13.7　ppb,　5.1　ppb,　7.7　ppb,　12.8　ppb,　and　3.3　ppb　in　July　and　13.2　ppb,　2.0　ppb,　5.7　ppb,　6.6　ppb,　and　1.0　ppb　in　January,　respectively,　on　a　monthly　average.　These　apportionment　results　match　well　with　the　2013　VOC　emission　inventory　calculated　by　this　study,　but　also　presented　significant　seasonal　differences　in　the　petrochemical　industry　and　gasoline　evaporation,　in　which　VOC　emissions　strongly　respond　to　environmental　temperature.