| Non-methane hydrocarbon (NMHC) play a very important role in the formation of ozone. The concentrations, compositions, and diurnal variation of NMHC were measured in July and August of 2014 in Dalian City. Continuous samples were collected in Dalian and were analyzed via gas chromatography. The results show that the annual mean concentration of total NMHC (TNMHC) concentrations was 80.7×10-9±62×10-9. Alkanes were the most abundant components, accounting for 64% of the TNMHC, followed by alkenes, aromatics, and acetylene, which accounted for 19%, 16%, and 1%, respectively. n-Decane, ethene, and octane were the top three species in Dalian City, and the diurnal variation of NMHC in this area was obvious. The ozone formation potential (OFP) results show that the contribution of aromatics to the OFP in Dalian was the largest, and ethylene, m-ethyltoluene, and p-ethyltoluene were the most important contributors to the OFP in this area. Principal component analysis (PCA) was used to identify the sources of the VOCs. Six sources were resolved by the PCA:solvent usage, LPG, traffic sources, biogenic sources, petrochemical refining, and aged air transportation.