Abstract: In view of the demand of offshore oil and gas engineering for the stability of energy supply, many energy supply systems coordinated by offshore generator units and onshore power grid have been established one after another. The establishment of a coordinated and optimized operation mode of offshore generator units and onshore power grid can improve the reliability of energy supply and reduce carbon emissions. Therefore, this paper proposes an energy-reserve cooperative optimal scheduling model of offshore multi-platform and onshore power grid energy supply system. At the same time, to cope with the independence between the offshore multi-platform energy supply system and the onshore power system, a distributed solution framework of the cooperative dispatch model is proposed on the basis of alternating direction method of multiplier（ADMM）. In order to ensure the convergence of the distributed solution algorithm, the second-order cone relaxation technology is used to relax the power flow constraints of offshore platform, and the model is transformed into a convex optimization model. The results of the numerical example show that, the cooperative energy supply system with offshore multi-platform and onshore power grid can effectively promote the consumption of renewable energy while protecting the information privacy of shore power system and offshore platforms.