Abstract: Oilfield hydrogeochemistry has been successfully used in directing the oil-gas exploration in many depressions. In recent years, the study on the interaction between water and the enclosing rock material is emphasized and has made significant advances. However, there are few studies on the deep oilfield water quality and hydro-geochemical environmental influence resulted from human activities. This article analyses the water quality features and their regular evolutional patterns in course of exploitation in the Renqiu Oilfield. The results of research indicate that the injected water has an obvious effect on the scattering and mixture of oilfield water which could make the water-rock interaction in the oi1 strata out of balance and change the original hydrogeochemical environment. The obvious difference in some ionic content between the real values and those calculated by the nomograms has demonstrated that physical mixture and geochemistry are closely related to each other.