Using the parameters which were obtained by ab initio HF(STO-3G) MO method，the mechanism of the reaction of t-butyl hydroperoxide(BHP)with N，N-dimethyl aniline (DMA) was discussed．The reaction is composed of three different reactions as follows： 1．Attack of N of DMA on O1 of BHP to give a N-oxide(Scheme 1，in Text)， 2．Formation of a hydrogen bond type complex (Scheme 2，in Text)． 3．Attack of N of DMA on O2 of BHP to give free radicals (Scheme 3，in Text)． The perturbation energies which were calculated by the klopman’s equation(Eg．(1) in Text) were 0.2276，0.1687 and 0.2065 eV in the cases of (1)，(2) and (3)，respectively．Accordingly，it was concluded that all the reactions may proceed simultaneously．