High standardization is the development trend of international investment rules. This paper studies the“black box”mechanism of“heterogeneity”of international investment rules by constructing the“BIT index”. The results show that: high standard bit can promote the flow of FDI; the investment of developed countries to developing countries is significantly affected by the high bit standardization; the investment of developing countries to developing countries is not significantly affected; the investment of developing countries to developed countries is positively affected, but not the“post border”effect of developed countries; the national governance and financial opening of developing countries is closely related to the development of host countries. Financial openness has a positive effect, and the lower the degree of economic freedom is, the more“post border”effect is. The study has implications for China to deal with the“high standardization”of international economic and trade rules, participate in the formulation of international rules and implement the reform of domestic system.