The last mile problem of rural logistics has hindered the smooth flow of"industrial goods to the countryside"and"agricultural products to the city",bringing inconvenience to the production and life of rural residents.As an innovative model,the"integration of transportation and postal services"emphasizes the joint construction and sharing of transportation and postal express in terms of operation mechanisms,infrastructure,transportation routes,and operational information.By accelerating the construction of an intensive,efficient,and sustainable rural transportation service system,it is expected to become an effective path to solve the last mile problem of rural logistics and promote integrated urban-rural development.Therefore,it has received wide attention and evolved into a national action aimed at better meeting the travel,freight logistics,and delivery service needs of rural residents.The theory of multi-source flow is an effective explanatory tool for policy processes.By using this theory to analyze the agenda-setting process of the integration of transportation and postal services policy,the essence of the development of this integration can be better grasped and the underlying mechanisms that have led to the integration of transportation and postal services becoming a national action can be better explained.It also provides insights for the adjustment and improvement of subsequent policies related to the integration of transportation and postal services.This paper finds that the evolution of the integration of transportation and postal services policy is the result of the combined actions of problem flow,policy flow,and political flow,going through the development process from the formation of ideas to the establishment of institutions and then to national action.The low passenger load rate of rural passenger transport,the underdeveloped rural logistics,and the inefficient performance of existing strategies constitute the problem source flow,providing a rational basis for the"integration of transportation and postal services"policy.The attention of the central government to rural work and changes in national sentiment constitute the political source flow,providing political guarantee for the policy.The suggestions of experts and scholars,as well as the active exploration of government departments,constitute the policy source flow,providing feasible solutions for the policy.The convergence of the three major streams mentioned above has promoted the opening of the"policy window"for the integration of transportation and postal services,as well as the introduction of policies such as the"Opinions on Deepening the Integration of Transportation and Postal Express to Promote the High Quality Development of Rural Logistics",making the promotion of the integration of transportation and postal services a continuously deepening national action that combines top-down and bottom-up approaches.To ensure implementation effectiveness,subsequent policy adjustments and improvements should further focus on the problem source flow,identify the constraints of the development of integration of transportation and postal services,utilize the political source flow to highlight the public orientation of the development of integration of transportation and postal services,optimize the policy source flow to improve the policy system for the development of integration of transportation and postal services,and grasp the"policy window"to promote the implementation and refinement of integration of transportation and postal services work,employing a variety of measures to fully unleash the basic support role of integration of transportation and postal services for the high-quality development of rural logistics.