Based on the research paradigm of the innovation chain and considering the supporting effect of the innovation environment, this study constructs an intrinsic mechanism model and evaluation index system for national innovation capability (NIC) along the “science-technology-industry” pathway under environmental support. Using this framework, we quantitatively assess the NIC levels of 20 major countries from 2011 to 2021. Furthermore, utilizing the relational data analysis paradigm and employing QAP method, we empirically examine the determinants of NIC disparities. The results indicate that all 20 countries exhibited growth in innovation capacity, with the United States maintaining a leading position throughout the period, while China demonstrating steady advancement, surpassing Japan to rank second in 2018, and market commercial maturity, international innovation cooperation, innovation institutions, openness to trade, and human capital and research, have significantly contributed to the disparities in national innovation capability. Among these factors, commercial maturity had the greatest impact on the differences in national innovation capability from 2016 to 2021. Accordingly, this study proposes harnessing the synergistic effects of the innovation chain, balancing domestic and international factors, and promoting the commercial application of innovation achievements to enhance national innovation capability and narrow gaps among countries.