We have reported that phenyliodonium diacetate[PhI(OAc)2]can serve as an eco-friendly mild oxidant for the epoxidation of alkenes in the presence of Mn(Ⅲ) complex of meso-tetrakis(4-methoxyphenylporphyrin) acetate Mn[(T4-OCH3P)P]OAc and imidazole in CH2Cl2.The amounts of the products(％) and selectivities are very dependent upon the electronic and steric properties of the starting alkenes.To evaluate the validity of this catalytic system for C—H activation,cyclohexane and ethylbenzene were oxidized under the epoxidation conditions.