In this paper, we introduce the concept of the national system of innovation, and discuss the possible measurement of its causes and consequences. The national system of innovation promotes techno-nationalism, arguing that appreciation of the social, institutional and economic environments is critical to explaining the generation and diffusion of technological innovation. The causes of the system remain unclear, as some support a priori framework and others focus on empiricism. In terms of the measurement of the system effect, patent is generally considered as effective, with the use of revealed technology advantage index prevalent in the literature. We conclude the paper by discussing some policy implications.