Green transformation is a necessary path on the road of green development of small and medium-sized enterprises (SMEs), and it is also a top priority for implementing the concept of sustainable development. The article innovatively proposes a green transformation evaluation method for urban housing projects based on the ecological footprint theory, which clarifies the resource use of urban housing projects during the construction process through the ecological footprint calculation, clarifies their ecological deficits, and solves the reduction of their ecological footprints through the green transformation. A double-difference model is introduced to analyze the impact of SMEs’ green financing and issuance of green bonds on the green transformation of urban housing projects. The short-term market response of green bonds issued by SMEs with green financing and the environmental benefits of urban housing projects are also verified. Between 2012 and 2021, the ecological footprint of urban housing projects in Guangdong Province increased by 36,273,366 nha, an increase of 137.04%, and the reduction of ecological footprint in the planning and construction phase of urban housing projects in Guangdong Province after the implementation of the green transformation strategy totaled 10,377.85 nha. Whenever the level of SMEs’ green financing and issuance of green bonds is increased by 1%, the reduction of ecological footprint of the green transformation of urban housing projects will be increased by 1%. Transformation of the ecological footprint reduction will be enhanced by 4.059. Relying on the green financing behavior of SMEs can promote the enhancement of the short-term market effect of the enterprise, and can also effectively enhance the utilization rate of green building materials in urban housing projects, and help the green transformation of urban housing projects.