Urbanization demands finer coordinated development of the urban human-earth relationship with high quality. Although a large number of studies have explored the long-term and large-scale coupling effect of urbanization and eco-environment, there is a lack of finer spatiotemporal method and assessment. Therefore, this paper proposes a monthly-scale pixel-based coupling coordination degree (CCD) model, aiming to explore the relationship between urban socioeconomic activity intensity (SAI) and regional eco-environment (REE) in Beijing during the period of January 2018 to May 2020 based on nighttime light data and MODIS images. The results show that the SAI in Beijing has shown a trend of increasing, and the overall REE was relatively stable during the investigated period. The CCD between SAI and REE in Beijing has been improving both spatially and quantitatively. Until May 2020, more than 50% of the human activity areas were in a state of high-level coordinated, and the mean CCD reached a basic-coordinated level. A schematic model is further built to explain the characteristics and process of coupling coordinated interactions between socioeconomic activity and eco-environment. The inner-annual micro-scale analysis and assessment provide theoretical support for fine-scale monitoring and high-quality urban development planning and policies from decision-makers.