Abstract: Effects of Cd(Ⅱ)and Zn(Ⅱ) on growth and content of polysaccharide as well as chlorophyll and protein were studied in alga Nitzschia closterium.The alga showed to some extent tolerance to the two metals which did not show significant effect on the growth of the alga at lower than 3.0,and 1.0 mg/L for Cd(Ⅱ)and Zn(Ⅱ)(P0.05).However,significant inhibition of the growth in the alga was observed at the metal concentrations of more than 3.0,and 1.0 mg/L(P〈0.05).Cd(Ⅱ)refrained the synthesis of protein in the algae while there was no evident effect of Zn(Ⅱ) on the protein synthesis in the alga(P〉0.05).Cd(Ⅱ)and Zn(Ⅱ) promoted the synthesis of polysaccharide and chlorophyll in the alga at concentration of less than 3.0 mg/L.