Abstract: As the primary pollutant in the Changjiang River Basin, phosphorus has a wide range of pollution sources and a complex composition, making it difficult to achieve accurate source tracing.Focusing on the Gaogang Port area of Taizhou City, we analyze the compositional characteristics of phosphorus in typical tributaries and estuaries discharging into the Changjiang River.Through phosphorus speciation analysis, 3D fluorescence spectroscopy, and high-resolution mass spectrometry (HRMS), coupled with a Principal Component Analysis-Absolute Principal Component Score-Multiple Linear Regression (PCA-APCS-MLR) model, we systematically identify phosphorus sources and their spatiotemporal distribution patterns.The results showed that: ① The disturbance on bottom sediments by wind waves and ships navigation, which led to an increase in particulate phosphorus near the shore, was the main factor contributing to the recent rise in total phosphorus at the research area.② The orthophosphate concentration showed a slight change along the area, indicating a low potential of industrial pollution.③ The fluorescent materials in the watershed were predominantly humus, showing a high degree of pollution homogeneity.④ With the use of high-resolution mass spectrometry to accurately analyze the characteristic fingerprints of organic phosphorus, the PCA-APCS-MLR pollution source contribution model was constructed, and it was concluded that domestic wastewater, material chemicals, agriculture, pharmaceutical chemicals, other industrial pollution and other sources contributed 47%, 5%, 3%, 1%, 1% and 43% to the total phosphorus pollution, respectively.The main sources of phosphorus at the Gaogang Port were bottom sediments and nearshore inputs.By analyzing the compositional characteristics of phosphorus at the estuaries of typical tributaries flowing into the Changjiang River and constructing a PCA-APCS-MLR model to quantify the source tracing technology of total phosphorus pollution, this study provides a reference for source tracing phosphorus in rivers.