Volatile organic compounds (VOCs) are important precursors of ozone and atmospheric particulate matters.In this study,98 VOCs were measured by online Gas Chromatography-Mass Spectrometer (Online GC-MS) from May to June in 2018 at a regional site in Taizhou,Jiangsu province.The compositions and diurnal variations of VOCs in Taizhou were analyzed,followed by a parameterization approach to calculate primary emissions and secondary formation of aldehydes and ketones.Source apportionment was conducted using the EPA Positive Matrix Factorization (PMF 5.0),while the Ozone Formation Potential (OFP) was calculated using the Maximum Incremental Reactivity (MIR).The results indicated that alkanes accounted for the highest proportion of VOCs in Taizhou,followed by aldehydes and ketones.The diurnal profiles of alkanes,alkenes,halogenated hydrocarbon,and aromatics were similar.The parameterization method demonstrated that aldehydes mainly came from secondary formation,while ketones mainly came from primary emission.PMF model results showed that VOCs in Taizhou were mainly influenced by vehicle emission,solvent volatilization,biomass combustion,and other industrial or natural sources.OFP results indicated that alkenes were predominant,accounting for 34.18% of the total ozone formation potential.As a result,measures of reducing industrial emissions and the use of solvent will play an important role in air pollutant control strategies of Taizhou.