Natural attenuation of BTEX and characteristics of the water in the study are researched in this paper. The study not only obtain the attenuation rules of BTEX over time, but also the rules of the redox materials of the contaminated groundwater over time. From the study, we reach conclusion that the redox conditions is changed with the increasing pollution of BTEX and the oxidation condition changes into reducing condition. With the changing of the redox condition, there take place a variety of redox reactions. The materials of oxidation, such as O2, NO3-, Fe3+and SO42-, are transformed into reduction materials, such as NO2-, Fe2+, S2- and so on. In this process, the components of BTEX are degradated by micro-organisms which using the oxidation materials as electron acceptors.