Abstract: The Hydrological Change Indicators (IHA) can comprehensively describe the hydrological regime of rivers. However, there is a certain overlap of information between the numerous indicators, which limits their widespread application in the fields of hydrology and aquatic ecology. Based on the daily runoff data of Lijiadu Hydrological Station in the lower reaches of the Fu River from 1953 to 2018, ecologically relevant hydrological  indicators (ERHIs) were preliminarily selected by principal component analysis (PCA), and the key ERHIs were further selected by combining the random forest (RF) importance scores of indicators under different labels. The evolution and influencing factors were also analyzed emphatically. The hydrological and meteorological variation points in the lower reaches of the Fu River were in 1962, 1984, and 2002. Based on this, the research period was divided into the reference period and the first, second, and third impact periods; Based on the PCA method, 8 ERHIs were initially selected, and the RF importance score was used to further optimize the minimum 30 day average flow, January average flow, and April average flow of three key ERHIs; During the three impact periods, the overall hydrological changes of key ERHIs in the lower reaches of the Fu River were 31%, 24%, and 50%, respectively; Among them, the minimum 30 day average flow rate showed moderate to high changes in each impact period, and experienced two decreases in the first and third impact periods, respectively. This was considered to be related to the continuous expansion of the number and scale of water conservancy engineering projects in the river basin; After the construction and operation of Hongmen Reservoir in the 1980s, the average flow in April during flood seasons was effectively reduced, while the average flow in January during dry seasons showed a slight increase; After the 21st century, key ERHIs in the lower reaches of the Fu River showed a downward trend due to climate change and urbanization processes. After PCA-RF screening, the IHA system in the lower reaches of the Fu River was greatly simplified, which helped to grasp the key indicators and provide important reference value and significance for ecological restoration and water resource optimization.