The characteristic and theoretical significance of this paper is to try to quantify the relevant policies of the provinces along "the Belt and Road" to determine the policy measure strength and policy guarantee strength based on designing the scoring standards of policy effectiveness, policy measure and policy guarantees.The relationship between the policy strength and the economic openness of provinces along "the Belt and Road"is discussed in detail, the differences between the eastern and western regions and the moderating effect of policy guarantee intensity on the relationship between policy intensity and economic openness are discussed. The study finds: 1) Policy measures strength can positively promote the improvement of economic openness.2)In provinces with economic openness higher than 10%, the policy guarantee strength is positively regulating the relationship between the policy measure strength and the economic openness improvement, and there is a complementary relationship between the policy measure strength and the policy guarantee strength.3) The capital financing strength of policy measure strength has the most significant positive impact on the improvement of provincial economic openness along the line. Policy communication strength has no significantly impact on the improvement of provincial economic openness.4) There are regional differences in the policy strength and the improvement of the economic openness, and the western regions pay more attention to the opportunities brought about by "the Belt and Road" initiative. It is necessary to make rational planning for policy communication, facility connectivity, trade smoothness, capital financing and popular feelings interlink. Making operational arrangements for the policy guarantee is also necessary.