Lakes Dianshan, Xiaoxingkai and Erhai represent different trophic status respectively, and each of them is suffering severe cyanobacteria blooms in summer. Nutrient enrichment bioassays were conducted in the fields to compare the effects of nutrients (N and P) on cyanobacteria growth in the three lakes in summer. Significant differences between/among the treatments of the experiments were tested by Univariate and LSD. The results showed that Lakes Dianshan, Erhai and Xiaoxingkai have significant responses to N, N and P, N in summer, and add N to the Lake Dianshan and Lake Xiaoxingkai with low N:P ratio which may cause cyanobacteria(Microcystis) blooms easily, while N and P interaction may induce cyanobacteria bloom in lake(Lake Erhai) with high N:P ratio.