The exploration of low-carbon design and optimization methods for urban park green spaces is a critical issue in China’s urban public space construction and renewal during the “14th Five-Year Plan” period. It is also essential for achieving the goals of carbon peaking and carbon neutrality, as well as promoting sustainable urban development. By integrating low-carbon park design elements and the ecological characteristics of plants, this paper takes Xiaocao Park in Hohhot City as a case study to apply low-carbon design and optimize plant communities with high carbon sequestration capacity. Based on the full life cycle of urban park design, construction, maintenance, and management, strategies are proposed to address carbon emissions through design optimization. Based on the carbon sequestration capacity of tree species and their habitat conditions, four high carbon sequestration plant community patterns and optimization strategies are proposed: tree - shrub -grass, tree - grass, shrub - grass, and groundcover types. These patterns are applied to various areas of Xiaocao Park, including the sparsely forested grassland, recreational activities, rain garden, ornamental grass sea, and pathway planting areas, to explore design and optimization approaches for low-carbon urban park green spaces. This study presents implementation strategies for low-carbon design and high-carbon sequestration plant community optimization in Hohhot’s park green spaces, providing both theoretical and practical support for achieving the “dual carbon” goals and promoting urban sustainable development.