Overseas oil and gas projects are influenced by investment environment, fiscal terms and technological progress. They have extensive interaction effects, and have important impact on economic evaluation and portfolio optimization of projects. Based on the three types of interaction effects, this paper analyzes the resources interaction effect, benefit interaction effect and the technical interaction effect of overseas oil and gas projects, and establishes the maximum benefit or minimum risk model of offshore oil and gas project portfolio based on interaction effect.The multi-verse algorithm is improved and applied to the solution of 0-1 nonlinear programming problem to optimize the oil and gas project portfolio.The results show that the interaction effects between projects will have an impact on portfolio selection, and the probability of the selection of projects with positive interaction effects will increase.The investment portfolio considering the interaction effect is better than the portfolio which does not consider the interaction effect in terms of profit and risk.It proves the importance of the interaction effect on the optimization of the overseas oil and gas exploration and development projects, and increases the scientificity of the investment decision.