Abstract: The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) and chlorophylla (Chl-a) con-centration were quantitatively reconstructed for the past 2000 years, based on the diatom-TP and diatom-Chla transfer functions. The shifts of diatom assemblages also mirrored the developments of aquatic plant, reflecting the characters of aquatic ecosystem evolution. The inferred epilimnetic TP concentrationfluctuated within a small range of 36 to 62 g/L, indicating the lake remained a relative stable mesotrophic status in the long historical period. The periodical variationsof the diatom assemblage and trophic status suggest a mitigatingfunction of shallow macrophyte-dominated lakes to nutrient input. The changesof lakestrophic status don t linearly respond to the human disturbance in the catchment. The dynamics mechanism of phosphorus in macrophyte dominated lakes, as inferredfrom diatoms, will provide a scientific foundationfor the prediction of trophic status change in a shallow lake, as well as the lake ecological restoration and management decisions.