In this paper, we take the mutual influences between the secondary industry agglomeration and economic growth in China’s county level as the research object. The panel data simultaneous equations models are specified to analyze the existence and change characteristics of the cyclical cumulative effects of industrial agglomeration and economic growth. The results show that industrial agglomeration and economic growth not only have a significant two-way relationship, but also they achieve their own cyclical cumulative effect based on the paths of “industrial agglomeration-economic growth-industrial agglomeration” and “economic growth-industrial agglomeration-economic growth” respectively. In terms of dynamics, compared to 2007~2013, the cumulative effect of agglomeration under the periodic impact of industrial agglomeration in 2014~2018 is weakened. The increasing diffusion effect leads to the decline of the role of industrial agglomeration in the economic growth cycle accumulation. In addition, the cumulative effects of different regions show heterogeneity characteristics. The cyclical cumulative effects of industrial agglomeration and economic growth are more significant in underdeveloped counties. In some economically developed counties, however, the industry isomorphism and the demand for the upgrading of industrial structure make the cumulative effect of industrial agglomeration become weak, and the crowding effect also makes the cumulative effect of economic growth decrease.