Even the United States，which has the most developed Internet economy，is facing the pressure of diminishing return on investment，which limits the role of Internet innovation in rebuilding growth momentum. The restructuring of US endogenous growth momentum by Internet economic development is closely related to the limitations of multi-level capital market development. The insufficiency of existing Internet innovation over-reliance on data and information externalities is reflected in the excessive narrowing of financial functions in the development of capital market，which concentrates on volatility risk hedging and fails to manage entrepreneurs’ individual risks well，thus undermining the financial support provided by private equity investment for entrepreneurs’ innovation. As a rising economy，the premature appearance of diminishing returns on investment and the existence of government failure costs caused by financial development path dependence in the development of Internet economy in China indicate that the task of rebuilding growth momentum is more arduous. Therefore，through a brief international comparison of Internet economic development between China and the United States，this report reveals the intrinsic links among Internet innovation，multi-level capital market development and growth momentum reconstruction.