A wide range of VOCs were measured both indoor and outdoor in 50 residences of Beijing in heating(December in 2011) and non-heating season (from April to May in 2012). Passive samples were deployed for 24hours at each site, and 102 compounds were quantified. Formaldehyde, acetone and acetaldehyde were mostabundant carbonyl compounds both indoor and outdoor with median concentrations of 32.1, 21.7 and 15.3μg/m3,respectively. Toluene (14.4μg/m3), ethane (17.6μg/m3), propane (11.2μg/m3), ethene (8.40μg/m3), n-butane(6.87μg/m3), and benzene (5.95μg/m3) had the highest median concentrations. Seasonal variations were observedwithin different compounds. Carbonyl compounds had higher concentrations in non-heating season both indoorand outdoor, while alkanes, alkenes, halohydrocarbon, aromatic compounds showed a somewhat increase inheating season. Most of the investigated VOCs had indoor/outdoor (I/O) concentration from 1 to 10, up to 100 forseveral compounds, indicating sources in the indoor environment are prevailing.