Urban agglomeration is not only the main form of new urbanization, but also the incubator of innovation. Theoretically, there is a complex interaction between urbanization subsystem and innovation subsystem in urban agglomeration. The Beijing-Tianjin-Hebei urban agglomeration is a national-level urban agglomeration designated by the national new urbanization planning, and it takes "the new engine of national innovation-driven economic growth" as its core function positioning. Therefore, exploring the coupling relationship between urbanization process and innovation and development of Beijing-Tianjin-Hebei urban agglomeration is beneficial to understand the relationship between urbanization and innovation and the development of this urban agglomeration. The comprehensive evaluation index system of urbanization and innovation is constructed by combing the internal theoretical relationship between two subsystems of urbanization and innovation. With the help of coupling coordination degree model and geo-detector factor detection method, this paper analyzes the evolution process and mechanism of coupling coordination relationship between urbanization and innovation in the Beijing-Tianjin-Hebei urban agglomeration. The findings: (1) The comprehensive level of urbanization and innovation in the study area presents a trend of steady growth, and the coupling and coordination relationship between urbanization and innovation also develops in a good direction on the whole, but the comprehensive level and coupling relationship are different in space. Specifically, the gap between the high level of Beijing and Tianjin and the overall low level of 11 cities in Hebei is obvious. (2) The Beijing-Tianjin-Hebei urban agglomeration has been characterized by the coupling coordination type of innovation lag since 2007. Moreover, most of the cities in recent years show the type of coupling coordination of innovation lag, which can be clearly concluded that the main reason for the coupling coordination level of this urban agglomeration in the past period of time is that the innovation level is relatively inadequate to support the urbanization. (3) The interaction between urbanization and innovation in the Beijing-Tianjin-Hebei urban agglomeration is very significant, especially the impact of economic urbanization and social urbanization on innovation, and the impact of innovation resources on urbanization is more prominent. It is also found that the role of innovation ability in promoting urbanization is relatively inadequate during the study period. In the future, the key direction of promoting the coordination level of urbanization and innovation coupling in the Beijing-Tianjin-Hebei urban agglomeration is to accelerate the improvement of urban agglomeration and the comprehensive level of innovation in each city.