In present work we would like to propose a mechanism of photooxidation of 1,1-dimethylhydrazine with nitromethane in the triplet state. The point of interest in this reaction is reactivity of nitromethane, which varies in different excited states. We determined some energetic properties using MCSCF and DFT methods with 6-311G(d) basis set for all atoms. The interaction between nitromethane and 1,1-dimethylhydrazine in the triplet state proceeds very quick (the activation energy is 3.5 kcal·mol^-1) due to electrons are localized at oxygen atoms. Products of this reaction are: N-metylmethaneimine, molecular hydrogen and nitrogen and dimethylamine.