Non-methane hydrocarbons (NMHCs) are abundant volatile organic compounds in the atmosphere, their photodegradation produces reactive oxygen species which can react with NOx compounds and thus contribute to ozone formation. In marine surface waters, NMHCs are generally supersaturated relative to the atmosphere, thus marine emissions represent a significant source of NMHCs in the atmosphere.Seawater samples were collected monthly using a 5 L plexiglass water sampler from surface (<1 m) and subsurface (~1 m above bottom) layers at 14 study sites in Jiaozhou Bay during September 2016 and August 2017.Seawater NMHCs concentrations were measured with a customized purge and trap preconcentration setup coupled to a gas chromatography-mass spectrometer.