Under the guidance of the goal of “double carbon”, exploring the low-carbon design method of landscape architecture from the perspective of the whole life cycle has become an essential issue for the renewal of urban public space in China. This paper analyzes the main carbon emission factors of landscape architecture from four stages of landscape material production, construction, daily use, and maintenance, as well as abandonment and demolition, identifies the design influencing factors, and builds a carbon reduction technical framework for urban waterfront space renewal design that includes eight elements of “vertical, water, greening, path, materials, lighting, water supply, and drainage” and two dimensions of “inside and outside levees”. Taking the Jialing River wetland and riverside green space transformation in Yilong County, Sichuan Province, as an example, based on the project practice, proposed a detailed and operable low-carbon renewal design method and analyzed the implementation effect. The study aims to explore the realization of carbon reduction in the whole life cycle of landscape through refined design control, which provides a positive reference significance for the low-carbon construction practice of similar projects.