Stoichiometry of nitrogen and phosphorus is important for the study of freshwater ecology, as the level and ratio of nitrogen and phosphorus greatly influence ecosystem structure and function. To understand the feature of nitrogen and phosphorus stoichiometry in large reservoirs in South China, this study carried out a sampling program from January to December 2023 in a typical large reservoir (Gaozhou Reservoir). Multivariate statistics was used to analyze the factors influencing their spatio-temporal dynamics. The results showed that the average concentrations of total nitrogen (TN) and total phosphorus (TP) were (0.54±0.13) mg/L and (0.026±0.011) mg/L respectively, indicating the meso-eutrophic status of Gaozhou Reservoir. And the mass ratio of TN∶TP ranged in 5-59 (24±11), suggesting mostly P limitation and sometimes N limitation on primary production. The dissolved inorganic nitrogen (DIN) was higher than 0.13 mg/L, and the dissolved inorganic phosphorus (SRP) was lower than 0.01 mg/L, indicating mainly P-limiting for phytoplankton growth in the reservoir. Low SRP concentration (0.006±0.003) mg/L and stable DIN concentration ( about 0.6 mg/L) in bottom water indicated limited internal release, and external input was the main nutrient source for the reservoir. Particulate form was the main component of TP and TN. Thus, water temperature, water stability and phytoplankton were the main factors affecting the spatial and temporal distribution of nitrogen and phosphorus. High water stability reduced the influence of riverine nutrients on lucastrine zone, and resulted in more stable nitrogen and phosphorus stoichiometry. The results suggested that the external nutrients were the most important process regulating nitrogen and phosphorus stoichiometry and eutrophication in the large reservoir.