The effects of heavy metal ions on the growth of Microcystis aesuginasa have been investigated. The phosphate-limiting culture as a control is first carried out with CB media. The measured values of kinetic coefficients of Monod eq., μ_(max) and K, were 0.60 day^(-1) and 0.06㎎-P/ℓ , respectively. When heavy metal ions such as chromium, copper and cobalt are added to CB media, the specific growth rate of Microcystis aeruginasa increases while the level of heavy metal is still low. However, inhibition effect has been clearly appeared at above the critical (growthaccelerating) concentration. The critical concentration (Cm) varies with heavy metal ions. The measured values of Cm such as Cu and Co are found to be 0.2㎎ /ℓ and 0.4㎎ /ℓ, respectively. But, the Cm value of Cr is traceable. The type of growth inhibition is turned out to be noncompetitive-inhibition and the calculated growth inhibition constant of Cr, Cu and Co based on experiments have been 0.85㎎/ℓ, 3.23㎎/ℓ and 10.53㎎/ℓ, respectively.