The upper module structure of the offshore large-flow natural gas processing is complex, with numerous control equipment, high control requirements, and high safety requirements. The selection and configuration of the key equipment of the integrated control system directly affect the control performance and operation cost of the system. Based on this, considering the cost and failure rate of the key equipment of the integrated control system of the upper module of the large-flow natural gas processing, a multi-objective optimization model for the key equipment selection is established with low cost and high reliability as the optimization objectives. The weight between the cost and reliability is determined by Analytic Hierarchy Process (AHP), and the genetic algorithm of elite individual retention strategy is improved to optimize the model. The correctness of the proposed model and the effectiveness of the optimization algorithm are verified by taking the selection of the key equipment of the integrated control system of the upper module of a large-flow natural gas processing as a test example, which provides a theoretical basis for the selection of the key equipment of the control system.