Abstract: By using multivariate analysis for 14 parameters obtainded in 1983 to 1985 at the two sampiing stations (Ⅰ, Ⅱ) in Lake Donghu, Wuhan, the relationships between water-blooms and relevant ecological parameters were analysed, and the discriminant function of water-blooms at each station was yielded. The principal factor in relation to water-blooms are gross primary production and concentration of ammonia-N at station Ⅰ, and water temperature, nitrate con centration, chlorophyll a and COD at station Ⅱ. Regression analysis of phytoplankton indexes (chl a and pG) against several nutrients (ammonia-N, nitrite, nitrate, total-N, phosphate, to tal-P and silicate) demenstrate that the principal limiting factor for phytoplankton in Lake Donghu at present is nitrogen instead of phosphorus.