Urban green space has reached the stage of stock development. Achieving carbon neutrality in cities with limited green space has become a focus and challenge in research on the carbon sink benefits of urban green space, particularly through the rational layout of low-carbon green space patterns and the scientific configuration of plant communities to increase biodiversity. Meanwhile, in the context of rapid urbanization, improving the quality and efficiency of the green space system has become a core strategy to promote the green transformation of cities and achieve the goal of sustainable development. This study innovatively constructs a low-carbon design toolbox containing six major elements: terrain treatment, water system planning, architectural vignette design, plant configuration, road organization and spatial layout, and proposes specific design strategies for each component. Taking the Qinmo Flower Pond, located on the north bank of the Weihe River in Qinhan New City, Xixian New District, as an example, this study systematically examines the enhancement of the city’s green space carbon sink function and the optimization of emission reduction paths. Further, it proposes a low-maintenance plant It further proposes low-maintenance plants and landscape design methods to synergize the ecological benefits of carbon sinks with the functional benefits of landscape and minimize the maintenance costs, providing theoretical basis and practical guidance for the enhancement of the quality and efficiency of urban green space and the design of high carbon sequestration landscapes.