Detailed analysis on the relationship between environmental conditions and phytoplankton growth was carried out the Kamak Bay, Southern Korea from January to November in 1991. Physico-chemical factors (temperature, salinity, sigma-t, dissolved inorganic nutrients such as ammonia, nitrite, nitrate, phosphate and silicate, N/P ratio) were collected 3 times a week as well as biological factors (chlorophyll a, phytoplankton species composition and cell number). The principal component analysis(PCA) proved that high density of phytoplankton biomass occurred under the condition of high temperature(=low salinity) and high concentration of dissolved inorganic nutrients. As the results of multiple regression analysis(MRA) of biological factors on physico-chemical factors as explanatory variable, phytoplankton growth was found to be controlled by some specific factor such as DIN (dissolved inorganic Nitrogen, but dinoflafellates(=phytoflageilates) growth by DIP (dissolved inorganic phosphorus) in warm seasons.