This study took Beijing-Tianjin-Hebei, the Yangtze River Delta, and the Pearl River Delta as study areas. Based on correlation analysis of overlapping years in 2012 and 2013, a power function model was used to transform NPP-VIIRS NTL data(2012—2017) to simulate DMSP-OLS NTL data. We generated a temporally consistent NTL dataset of study areas from 1992 to 2017 (consisting of 1992—2013 DMSP-OLS NTL data and 2014—2017 NPP-VIIRS NTL data). By referring to the statistical data of urban built-up area, the optimal threshold of nighttime light was determined to extract urban scope. Based on this method, urban scope with insufficient economic vitality contained in the statistical data was effectively stripped off, while those low-grade,high-vitality urban areas that did not belong to the statistical scope were identified, which innovated the perspective of data application. Results show that: ① The contribution of county-level towns and cities of the municipal level to the economic vitality in three first-class urban agglomerations was different. The Beijing-Tianjin-Hebei had a vast hinterland, and county-level towns were an important part of the regional economic vitality. As a whole, they had the largest contribution in three first-class urban agglomerations. In the early 1990s, some county-level towns in the Yangtze River Delta had strong economic vitality. After 2005, it was lower than the Beijing-Tianjin-Hebei with the process of transforming county into urban district. Affected by the socioeconomic development and the division of administrative units, the contribution of county-level towns to the urban scope in the Pearl River Delta was always the smallest in three urban agglomerations. ② There were differences in the imbalanced characteristics of urban spatial expansion in three first-class urban agglomerations. The urban spatial expansion of the Beijing-Tianjin-Hebei was led by Beijing and Tianjin, which has formed a "dual-core" model. It has not yet formed a sophisticated urban system. The Yangtze River Delta and the Pearl River Delta had obvious urban agglomeration characteristics and stronger equilibrium. The path, direction, and distance of center of gravity migration reflected the different expansion intensity and behavioral model in three first-class urban agglomerations; ③ On the whole, urban spatial expansion pattern presented the characteristics of continuously expanding hot-spot regions and shrinking cold-spot regions. Specifically, hot-spot regions and cold-spot regions were relatively stable in the Beijing-Tianjin-Hebei, and the hot-spot regions had a strong centripetal agglomeration effect. The spatial patterns of the Yangtze River Delta and the Pearl River Delta has changed greatly and the regional core cities had a stronger driving role.