Urban green land plays an active role in the process of improving urban ecological environment and the harmony between human and nature. With the economic development, industrial progress and the improvement of people's living standard, urban greenness as the regulator of urban environment has been generally concerned. The dynamic monitoring of urban green land is conducive to scientific and effective urban management, and provides scientific basis and evaluation criteria for urban green land system planning. In this paper, we use remote sensing as the observation means to systematically carry out the research of urban green land ecological environment monitoring technology and analysis. Firstly, it introduces the pre-processing techniques of remote sensing data for urban monitoring, and selects the area method, grid cell method, buffer zone method and moving window method as the key techniques for spatial measurement of urban greenness spaces, and finally evaluates the ecological effects of urban green land with the greenness environment index model of urban buildings. This paper provides the key techniques and evaluation process of urban green space remote sensing in a more systematic way, which will play an important role in garden city evaluation, ecological city evaluation, garden planning, smart city and ecological city support, urban building planning, and sponge map city construction.