Abstract: Primary emissions from vehicles contribute significantly to urban PM_2.5 pollution. The high resolution mass spectra（MS） provided by Aerosol Mass Spectrometry（AMS） has proved to be a useful dataset for source apportionment of organic aerosols（OA）. However, the lack of source profiles of vehicle emission results in the large uncertainty in the source apportionment of traffic related sources. Vehicle chassis dynamometer tests were conducted to investigate reference spectra of primary emissions from gasoline vehicle with PFI engine. The most dominant fragments in the spectra are C_xH_y⁺ ions, which may be derived from fragmentation of fuel and lubricating oil of incomplete combustion. The relative contribution of different fragments as well as O/C ratio are influenced by engine condition. During the hot start, the primary aerosol are greater influenced by combustion-derived OA, which have a higher O/C ratio. The reference spectra of primary emission from gasoline vehicle were further compared with hydrocarbon like OA（HOA） resolved from ambient air. Their differences imply HOA cannot be considered as a surrogate of traffic related primary emission.