<p>Analyzing the changes of multiple ecosystem services (ESs) from an integrated perspective are conducive to maintaining the stability of regional ecosystems. Therefore, taking the Huai River Basin (HRB) as an example, we considered the basin’s carbon sequestration (CS), water yield (WY), and soil conservation (SC) to construct an integrated ecosystem service index (IES) incorporated with the principal component analysis to reveal the spatiotemporal variations of the integrated ecosystem service in the basin from 2001 to 2020. The result showed that the cumulative contribution rates of the first (PC1) and second (PC2) principal components were more than 70%, and the PC1 loadings were all positive, while the sign of the PC2 loadings was inconsistent. The increase of all ESs in the southern part of the basin constituted a concentric zone, while the decrease of WY and SC in the northern part constituted a disturbance zone. The IES exhibited fluctuating and increasing trends (<i>P</i> &gt; 0.05), with a rate of change of 0.01 yr^− 1. The increase in the good grade after 2013 was the primary contributor to the IES grade transition. Spatially, the IES exhibited a gradual decreasing trend from south to north, with decreases only in the and northwest and northeast. Climate change was the dominant factor in the changes of IES, and total solar radiation, vapor pressure deficit, and precipitation were the main driving factors contributing to spatial changes in IES. The combined effects of these drivers suggest that suitable climatic conditions positively impact IES. In summary, this study provides a new perspective for assessing integrated ecosystem service and serves as a valuable reference for formulating policies promoting sustainable ecosystem development.</p>