Petroleum plays an important part in modern industrial production. It is an important strategic resource related to national security. With the decrease of onshore oil reserves and the progress of offshore oil exploitation technology, offshore oil has been paid more and more attention. Improving the reliability of the power system of the offshore oil field group is of great significance to ensure offshore oil exploitation. In view of the actual characteristics of the power system of the offshore oil field group, this paper puts forward an evaluation method of the power system of the offshore oil field group taking into account load correlation.