Using NCEP/NCAR reanalysis data,ERSST v5 sea surface temperature data,and an atmospheric circulation model,we analyzed the mechanisms and relative contributions of tropical Indo-Pacific ocean SST anomalies to the high-temperature event in the middle and lower reaches of the Yangtze River basin during the summer of 2022.The study shows that the summer of 2022.recorded the highest temperatures in the middle and lower reaches of the Yangtze River basin in the past 40 years,with an area mean anomalous temperature of 1.52.℃.The spatial distribution of positive temperature anomalies in this region was highly uneven,with the maximum anomalies located to the west of the Henan-Hubei border.This positive temperature anomaly event was influenced by both La Niña and the negative phase of the IOD.After removing the ENSO and IOD signals,the anomalous temperatures in the middle and lower reaches of the Yangtze River were 1.23 and 1.37 ℃,respectively.When both ENSO and IOD signals were removed,the temperature anomaly was 1.13 ℃,indicating that tropical Indian Ocean and Pacific SST anomalies contributed 25.66％ to the summer high-temperature anomalies in this region.The atmospheric Matsuno-Gill response to the La Niña event caused an anticyclonic circulation anomaly from the middle and lower reaches of the Yangtze River to the Northwest Pacific region.The negative phase IOD event enhanced the subtropical high in the western Pacific by strengthening the easterly anomalies over the Maritime Continent.The strengthened western Pacific subtropical high favored maintaining anomalous subsidence motion in the middle and lower reaches of the Yangtze River basin,facilitating the occurrence of the high-temperature event.These results provide a scientific basis for understanding the extreme high-temperature events in the middle and lower reaches of the Yangtze River basin during summer.