Methyl tert-butyl ether (MTBE) and ethanol as gasoline fuel additives can enhance gasoline fuel octane value. This study evaluates the effects of these oxygenated additives (MTBE and ethanol) at 10% by volume on the main combustion intermediates in a low-pressure laminar premixed gasoline flame using synchrotron radiation. The photoionization mass spectra of three flames were presented, and the temperatures of flames were measured by a thermocouple. The relative concentrations of five typical combustion toxic species in the gasoline, gasohol, and MTBE/gasoline flame were compared. It is observed that ethanol and MTBE both delay the oxidation of aromatics in gasoline, and MTBE plays a more obvious role than ethanol, It is also shown that the addition of ethanol leads to an increased concentration of acetaldehyde, whereas the addition of MTBE has no significant effect on the concentration of acetaldehyde. The results obtained provide data for the analysis of intermediates and radicals in flames, which is of use in establishing the chemical kinetic processes of gasoline/oxygenated additive flames.