Abstract: Toxicity effects of pentachlorophenol(PCP)　under different mass concentrations(0,0.02,0.05,0.10,0.50,1.00 mg/L) on the growth,the contents of pigments and soluble protein of Scenedesmus obliquus decreased with the increase of PCP mass concentration.EC50 value for 24,48,72,96 and 120 h was 0.883,0.283,0.225,0.168 and 0.192 mg/L respectively.The growth of algae was almost completely inhibited when PCP mass concentration was higher than 0.50 mg/L.Meanwhile,the mass concentrations of pigments and soluble protein in 96 h-culture algae solution were also determined.The total levels of pigments,soluble protein and the ratio between chlorophyll a and b declined as PCP mass concentration increased.The susceptibility of pigments to PCP followed the order of carotenoid>chlorophyll a>chlorophyll b.There was an obvious linear relationship between the contents of pigments and soluble protein (r=0.793,n=6)。