Abstract: Addressing the wide gaps in regional development is a key issue in the stage of highquality development.Based on countylevel panel data from 2010 to 2019,using the policy shock of the development strategy of the Yangtze River Economic Belt (YEB) and the DifferenceinDifferences(DID) method with an intensity index,this paper finds that,on average,the interactive influence mechanisms of policy dividends and geographical endowments significantly promoted regional economic development,making the GDP and GDP per capita of the treatment group about 2.49% and 2.66%,respectively,higher than the control group.This regional disparity of economic growth mainly comes from the development of the secondary and tertiary industries.The mechanism analysis shows that the development strategy of the YEB has led to a sharp fall in freight costs.With the decrease in freight costs,there are three major effects: industrial agglomeration effect,factordriven effect,and demanddriven innovation effect,which promote the changes in industrial structure and form the regional disparity of economic growth.Further heterogeneity analysis shows that the middle and upper reaches and the regions with low inland waterway transport endowment of the YEB have faster economic growth rates.Institutional reform should be implemented according to the geographical endowments of different regions,which can boost the economy under economic pressure,address the wide gaps in regional development between different regions,and jointly promote highquality economic development in China.