Abstract: A low-pressure premixed gasoline/oxygen/argon flame was studied by using molecular-beam sampling mass spectrometry combined with a tunable synchrotron radiation photoionization technique. The photoionization time-of-flight mass spectrum of gasoline/oxygen/argon in the flame was recorded and the ionization energies of some species were detected. Compared with the ionization energies in literatures, the isomers were uniquely identified. The reaction process of five typical hazardous products was empirically analyzed by species concentration profiles. The experimental results are helpful in establishing the kinetic modeling for a gasoline/oxygen flame.