The interaction of production factors among cities plays a significant role in the spatial expansion of urban agglomerations. Meanwhile, it drives the change of urban agglomerations from a single-level flat regional space into a multi-level network system. The shift of Chinese urban agglomerations from segregated regions to spatial networks has become the focus of academic research in recent years. Studies have advanced an argument that the relations of traffic and industry between each city-pair not only provide internal dynamics for the spatial expansion and hierarchical organization of urban agglomeration, but also describe the development state of urban agglomeration. Based on the perspective of coupling relationship between traffic and industry, this study identified the multi-level spatial structure and development scope of the Beijing-Tianjin-Hebei urban agglomeration by spatial network analysis, gravity model, and Multi-level Spatial Structure Tree (MSS-Tree), using socioeconomic data, traffic volume data, and enterprise network data. We first selected the municipal districts of Beijing, Tianjin, Shijiazhuang, and Tangshan cities as four radiation centers based on the result of comprehensive strength calculated by factor analysis. Then we combined the gravity model with the MSS-Tree algorithm, and the result shows that continuity, hierarchy, and difference coexist in the theoretical spatial structure of the urban agglomeration. Meanwhile, we applied traffic volume data and enterprise network data to the MSS-Tree algorithm, and the result shows that current spatial structure presents the characteristics of fragmentation, hollow, and jumping, which is quite different from the theoretical structure. According to the comparison between the current scope and the theoretical scope, the current development scope is smaller, and there is obvious an "island and cave" phenomenon in the radiation area of radiation centers, which show contiguous distribution of metropolitan shadow areas. For the four radiation centers, there is a lack of mature sub-centers around Beijing; the spatial scale of radiation area around Tianjin is shrinking greatly because of the polarization effect of Beijing; and the radiation areas around Shijiazhuang and Tangshan are poorly developed, indicating that the two cities need to strengthen their own economic construction. Further, the comparison between traffic and industry radiation areas reveals the phenomenon that traffic develops first while industry lags behind. The unbalanced coupling relationship between traffic and industry leads to low coincidence degree in radiation areas of these two factors. The leading role of traffic accelerates loss of production factors from small or medium-sized cities, thus forms the poverty belt around Beijing and Tianjin. From the perspective of traffic-industry coupling relationship, this study explored the existing problems and their mechanism, which is significant for efficient synergy in the spatial development of urban agglomerations. Finally. Based on the perspective of local government, this article proposed regional development strategies of integration from bottom to top and expansion from inside to outside.