Regional differences in green level were reduced, and gaps within group were far larger than gaps between groups.
Green level in 54.58% of CBAs indicated mutation phenomenon, and the green level in most of these CBAs improved after the turning point. Average green level in China’s CBAs experienced a V-shaped change. Results showed that during 2001–2018, GI and its different aspects of green coverage (GC), green stability (GS), and the balance of the greenness distribution (BGD) were generally high in South China and low in North China. mutation test, trend analysis, spatial autocorrelation, Theil index, and scale variance). Spatiotemporal pattern, regional differences and geographical variances of green level during 2001–2018 in China’s CBAs were explored using geographic analysis methods (i.e. GI can be measured by integrating MODIS EVI data and metrics including green coverage index, nearest neighbor index, and coefficient of variance. In this study, an innovative green index (GI) was developed for evaluating green level in CBA from three aspects of “quantity-stability-balance”. With the acceleration of urbanization since the 21st century, the level of green vegetation in the core built-up area (CBA) and its response to human activities are of great interest. Urban built-up areas are the core area of global population agglomeration, where the interactions between human beings and the surrounding ecological environment supporting their survival are particularly intense.