At present, excessive concentration and infiltration of capital and other behaviors of “capital conglomerates” pose a serious threat to high-quality economic development, so timely capital regulation for promoting common prosperity has great theoretical and practical significance. The theory of capital control in ancient China, Marx’s critical thought of capital, Sun Yat-sen’s thought of capital regulation and MAO Zedong’s thought of capital regulation have provided sufficient theoretical self-restraint for the new era. The view of capital of socialism with Chinese characteristics always adheres to the orientation of common prosperity. Combining with the existing ideological basis and the current realistic background, this paper analyzes that capital regulation in the sense of the new era has the double connotation of preventing excessive concentration of capital and preventing disorderly expansion of capital. From the perspective of the relationship between restrained capital and common prosperity, capital regulation can promote the sustainable growth of production and the fair sharing of achievement by effectively curbing the inequality of capital and its income and optimizing the allocation of factor resources. Its main policy tools are to improve the abstinence capital tax framework and strengthen the platform economy anti-monopoly. At present, China still faces many practical difficulties in capital regulation, such as great resistance of capital regulation, capital flight, imperfect capital tax system, vague boundary of capital expansion, high incidence of fraud in the field of internet capital, and imperfect related supporting reforms. The capital regulation measures and effects of some developed countries provide useful experience and lessons for China: The design of China’s capital regulation system should fully consider the reality of economic development, pay special attention to ruling out the understanding of international capital tax competition, better play the role of the promising government and the national system, and improve the capital management efficiency. Specifically, we should further strengthen the guidance of public opinion to reduce the resistance of control, prudently open the capital account to prevent capital flight, speed up the construction of a multiple-type and progressive capital tax and “data tax” system, improve the negative list of capital expansion and strengthen anti-monopoly punishment, and constantly improve relevant supporting services, so as to better deal with the relationship between the role of capital behavior and growth efficiency and development fairness, thus promote common prosperity. This paper puts capital regulation under the overall framework of common prosperity, which provides a useful reference for further regulating capital behavior and guiding the healthy and orderly development of capital in the new era, and provides a valuable interpretation for understanding the internal relationship between restrained capital and common prosperity.