This book analyzes the national economic system with systematic theory and defines the object of research as "the movement and laws of the national economic system." This book also proceeds a more in-depth study of the four relations concerning the reproduction. It examines the interdependent relations among population, economy, society, resources and environment, as well as the interactions among demographic reproduction, material product reproduction, spiritual and cultural reproduction and ecological environment reproduction from a dynamic perspective. It also explores the establishment of a system in which the four kinds of reproduction promote mutually, interact positively and develop harmoniously. Besides, this work pays attention to the management of the national economy and emphasizes the role of institutional innovation in promoting the performance of the national economy. It explains the connotation of institutions, their formation, their changes and innovations. And it dissects that the institutions, as an incentive mechanism, play a significant role in stimulating the vitality of human, of enterprise and the whole economy, which contributes greatly to the optimal distribution of resources, technological innovation and the effective growth of the national economy.