The influence of exogenous nutrients on algal growth was studied in Lingshan Station of Taipinghu Reservoir,Anhui Province during the algal growth season of 1992~1993.Two short-term algal bioassays, i.e., algal growth potential (AGP) test and black-light bottle test-the main experimental method of determining nutrient limitation for phytoplankton and green macroalgae-were performed integratedly in various seasons in the site experiments.The main additive used included phosphorus (NaH₂P0₄) and nitrogen (KN0₃).The algae was Scenedesmus obliqus. According to these experiments, the results show; (1) The two methods were effective to reveal the trophic state of Taipinghu Reservoir and the results can be extended to large and medium reservoirs in the Changjiang River Basin.The respective one-side defect coaid be avoided and the two methods be used integratedly. (2) The nutrient limitation of algae varied widely during the study period.In early summer,only the addition of P evoked a clear increase in the growth of algae, revealing that P was the primary limiting nutrient of algal population, biomass and primary production.In late summer and autumn, neither the addition of P nor the addition of N stimulated algal growth as in early summer because of the relative deficiency of other nutrition by the dilution of rainwater in summer rainy season, and the limiting action of P was declining. (3) The optimum P concentration for S.obliqus growth was 0.20mg/L. The aforementioned analysis can be used for guiding technique of artificial fertilization in large water bodies.Many nutritions should be supplied when P and N are added in late summer and autumn in the Reservoir.