||Rapid urbanization has generated enormous pressure on natural resources. This study illustrates urban expansion in the Jing-Jin-Ji region and its influence on vegetation primary productivity. Tempo-spatial correlations between a vegetation index and nighttime light intensity are discussed to assess the urbanization effect quantitatively. The results show that: (1) From 1998 to 2018, urban areas gradually expanded outward from their original conglomerations. (2) In the past 20 years, Beijing and Tianjin have developed in different ways. The surrounding satellite cities have mostly developed concentrically, although some cities in Hebei province have developed more linearly. (3) The average primary productivity of the study area in 1998, 2003, 2008, 2013, and 2018 was generally lower than that of non-urban regions of the same year. (4) During the period from 1998 to 2018, the primary productivity of vegetation in the urban built-up areas increased, and the condition of the plant improved.