With the geographical expansion of economic development and the evolution of production method, urban agglomerations have become the new arena for innovative activities. Current research has studied the causation, performance, and synergy of innovative activities within agglomerations from both spontaneous and institutional perspectives. This dissertation chooses the Yangtze River Delta Urban Agglomeration (YRDUA) as the case study. Although previous scholars have examined the evolution of regional innovation in YRDUA, few of them linked the changes with agglomeration policies. This dissertation aims to determine how spatial planning policies influence regional innovation capacity within an urban agglomeration over time. In this context, urban agglomeration is defined as a highly development spatial pattern of cities who compete while also seek collaboration with each other, and regional innovation capacity (RIC) is defined as the acquisition, absorption, and transmission of knowledge and technology that improve the output of products and services within a region. The study is based on the quantitative analysis of indices measuring innovation capacity and policy reviews. The evaluation framework is selected from the China Regional Innovation Capability Report and policies are retrieved from official public websites. Data are processed with the Principal Component Analysis under SPSS. The results indicate that although the ranking of regional innovation capacity did not change, their divergence has significantly narrowed. Further analysis suggests that policies have influenced the determinants and overall performance of RIC. On this basis, it is recommended that future policies aim at promoting regional comparative advantage and further exploring the utilisation of market mechanisms. Further research is needed to establish a more context-specific evaluation framework and identify the policy effect on the trickle-down of innovation capacities.