From September to October 2023, a study was conducted to analyze the distribution characteristics and concentration levels of 19 odorants in source water and finished water from typical water treatment plants in key river basins of Jiangsu Province. The basins included the Yangtze River(Yangtze River Basin), Tai Lake(Yangtze River Basin), Yi-Shu-Si(Huai River Basin), and Huai River(Huai River Basin). The removal efficiencies of odorants using water treatment processes were further explored. The results showed that 5 out of the 19 target substances were detected. In source water, benzaldehyde(ND~2.8 ng/L), β-ionone(ND~3.1 ng/L), and β-cyclocitral(ND~7.0 ng/L) were detected, with detection rates of 75%, 25%, and 25%, respectively. In finished water, benzaldehyde(5.9~12.9 ng/L), hexanal(1.4~4.0 ng/L), heptanal(ND~4.3 ng/L), and β-cyclocitral(ND~3.0 ng/L) were detected, with detection rates of 100%, 87.5%, 50%, and 25%, respectively. None of the detected substances exceeded their odor threshold values. The main odorants detected in the water of key river basins of Jiangsu Province are aldehydes, among which hexanal, heptanal, and β-cyclic citral are related to algal metabolism, and benzaldehyde is related to fine chemical pollution. The advanced treatment process showed certain removal effects on β-cyclocitral and β-ionone, with removal rates exceeding 50%. The concentration of benzaldehyde in the finished water increased by 383.3% compared to the source water. Hexanal and heptanal were not detected in the source water but were found in the finished water. The elevated concentrations of benzaldehyde, hexanal, and heptanal in the finished water may be related to chlorination disinfection and ozonation processes in the water treatment. The Huai River exhibited the highest variety of odorants detected in source water(benzaldehyde, β-cyclocitral, and β-ionone) as well as the highest total concentration(37.5 ng/L). The Yi-Shu-Si and the Huai River, exhibited the highest variety of odorants detected in the finished water(benzaldehyde, hexanal, β-cyclocitral, and heptanal), and the Yi-Shu-Si had the highest total concentration(47.6 ng/L). The main odor-causing substances in the key river basins of Jiangsu Province are aldehydes. Although the detected concentrations of aldehydes are all below their odor threshold levels, their concentrations increase after water treatment processes, which warrants attention. The issue of odorants in the Huai River Basin should be prioritized as a key focus.