The auto-oxidation of hydrocarbons in fluidized catalytic cracked (FCC) diesel fuel was studied, and the products were analyzed by ultraviolet spectroscopy, infrared spectroscopy, and gas chromatography- mass spectroscopy. The results show that the auto-oxidation of hydrocarbons varied with different molecular structures. The tetralin, which contains two active H atoms (alpha-H), was easily auto-oxidized to hydroperoxide, and the concentration of hydroperoxide (Wt_(ooH))% increased to 5.01%, after being heated under the following conditions: a temperature of 373 K for 30 h with an airflow rate of 90-100 mL/min. Cetene, cetane, and 1-methylnaphthalene were very stable and could not produce hydroperoxides under the same conditions. Great co-oxidation existed between tetralin and cetene. The extent of auto-oxidization increased as the initial concentration of tetralin and the rate of airflow each increased. The auto-oxidation reactions were strongly inhibited by antioxidants such as phenols and thiols. The products from the auto-oxidation of hydrocarbons were mainly carbonyl and hydroxyl compounds. The mechanism of auto-oxidation was free-radical chain reaction. Controlling the auto-oxidation of active hydro-carbons in the FCC diesel fuel is one of the effective ways to improve the stability of diesel fuel.