Oil field exploitations have a considerable impact on environmental security. The method of oil field environmental security evaluation method should be introduced into oil field exploitations for protection of environmental security. The frame model of pressure-state-response (P-S-R) was selected for oil field environmental security evaluation. Assessment levels were classified into five levels according to the value of synthetical index (SI), which was determined by the calculation of information entropies and value assignment of analytic hierarchy process. Finally, quantitative assessments of oil field environmental security situation were presented.