Abstract: Automobile exhaust is one of the major anthropogenic emission sources of volatile organic compounds (VOCs). VOCs, which spread in the atmosphere environment, have high activity, involved in the formation of ozone reactions, and it is an important precursor of pollutants such as secondary organic aerosols. Gas chromatograph or gas chromatography mass spectrometer combined with pre-concentration, thermal desorption are usually used to detect VOCs, but pretreatment processes of samples with these methods are complex and time-consuming, which can’t meet the requirements of rapid, direct and on-line detecting. Currently, development of portable VOCs analytical instrument applied in the field, real-time and on-line detection is one of the important research directions of modern scientific instruments. A portable membrane inlet vacuum ultraviolet single photon ionization time-of-flight mass spectrometer was introduced in this paper, including membrane sampling inlet system, vacuum ultraviolet ionization source, orthogonal-acceleration and reflection time-of-flight mass analyzer, vacuum system, data acquisition system, etc. The results show that the mass resolution of the instrument is higher than 350, the mass precision is better than 1×10^-4, the limits of detection for benzene series are μg/m³ stability, the total weight of the instrument is less than 25 kg. The instrument was used in the automobile exhaust test in the open air. The relativity between variation trends of VOCs automobile exhaust emissions and the engine work status was preliminary explored, rely on the high temporal resolution of this instrument. It can be speculated that this instrument would be applied in the field of environmental emergency accidents, in situ monitoring for a long time, production process monitoring in chemical industrial park, fugitive emission of VOCs, and so on.