Methane is the major component of natural gas, and it is a harmful greenhouse gas (GHG). For years, the reduction of methane emission in natural gas industry has been an important topic globally. With the increasing global energy demand, natural gas, as a crucial source of clean energy, requires urgent attention regarding emission control and reduction. In practice, with the development of natural gas pipeline systems, areas that contain multiple operating natural gas pipelines are becoming more common than ever. This poses a new challenge and opportunity to emission reduction: how to balance the time and resources on these pipelines so that the overall inspection cost and methane emission level of leakages can be minimized. In this paper, for the first time, a multi-objective optimization is applied to explore the Pareto optimal schedule set for areas with single and/or multiple pipelines. This study provides an approach to calculating the longest inspection period that controls the annual emission at the permissible level and proposes the optimal inspection period factor (OIPF) that can make the best use of the inspection budget to achieve the minimum total emission of multiple pipelines in the area. In the case study, the optimized schedules achieve a 7.56% lower annual emission with the same inspection cost, or a 7.90% lower cost without increasing the emission level without adding any new equipment. The research results indicate that through scientific scheduling and optimization, methane emissions can be effectively controlled while significantly reducing operational costs. This dual benefit enhances both the environmental and economic performance of the natural gas industry.