Aiming at the problems of unclear assessment level，unfocused emphasis，and poorly targeted measures in the safety risk assessment practice of large-scale petrochemical port areas，this paper constructs an indicator system based on inherent risk factors，risk prevention and control capability as the basic indicators，and establishes the mathematic model of safety risk calculation based on the analytic hierarchy process （AHP）.Combined with the safety management status of large domestic petrochemical port areas，the classification standards for security risks are proposed，and finally a quantitative assessment of the regional security risk level of large petrochemical port areas is realized. Empirical research is carried out by safety risk assessment of a typically large petrochemical port area，it is concluded that the regional safety risk is level III （larger risk）.