Based on the data of 26 cities in the Yangtze River Delta(YRD)urban agglomeration from 2016 to 2020,through the use of the super-efficient SBM model measure the input-output efficiency of infrastructure in the YRD urban ag-glomeration,this paper renders an analysis of its spatial and temporal evolution and explores its spatial correlation pattern with the help of the Kernel density estimation method.The results of the study shows that:(1)the infrastructure input-out-put efficiency of the YRD urban agglomeration as a whole has been improving continuously,and in terms of sub-region,the infrastructure input-output efficiency of Jiangsu and Zhejiang has been growing steadily,while Shanghai and Anhui have shown a"V"-shaped growth trend of decreasing and then increasing;(2)in the terms of spatial distribution,the spatial distribution of infrastructure input-output efficiency in the YRD urban agglomeration has significant differences,showing a distribution pattern of"high in the center and low at the edge",and the pattern of"one pole and two nuclei"in the region has basically been formed;(3)The kernel density curve has gradually shifted from a"single-peak"distribution on the left to an"M"-type bimodal distribution,and the phenomenon of"club convergence"in which the high and low values are clus-tered separately has appeared.In view of this,this paper proposes that it is a necessity to break down the barriers to the flow of resources and factors,promote the efficiency improvement according to local conditions,and strengthen the invest-ment in infrastructure,so as to comprehensively promote the efficiency improvement of the infrastructure of the Yangtze Riv-er Delta urban agglomeration.