JP-900 (C10H18) is a bicyclic, high-energy-density fuel being employed in aircrafts. In recent years, inspection of fuels refined by different processes has showed that noticeably higher peroxide concentrations exist in fuels, which have been severely hydrotreated. Hydroperoxide concentration was considered to be a parameter in fuel instability. Presently, Density functional theory (DFT) calculations were carried out to investigate the mechanisms of oxidation of JP-900 through hydroperoxidation. The total electronic energies of JP-900, and certain radicals and hydroperoxides originated from JP-900 were calculated. Their thermodynamic stabilities were discussed. The most feasible carbon center of JP-900 that would be oxidized through hydroperoxidation was assigned. It has been found that the hydroperoxides may decompose to different products having greater stability (possessing more negative total electronic energies). A variety of mechanisms including carboxylic acid (ester)-alkane, alcohol-aldehyde and ketone-alcohol decomposition mechanism were questioned. The probable decomposition products were determined and confirmed by thermodynamic calculations.