Abstract: Prorocentrum donghaiense, Chaetoceros decipiens and Prymnesium parvum were exposed to Decadienal (2E, 4E-Decadienal, DEC) which was a common toxic polyunsaturated aldehydes at different concentrations, the species and contents of photosynthetic pigments were monitored frequently.The HPLC results showed that 5, 8, 9 types of photosynthetic pigments were detected in P.donghaiense, C.decipiens, P.parvum respectively, in which there were four identical pigments.There was no significant difference in the concentrations of photosynthetic pigments of three species of algae with DEC at 1 mg/L.However, DEC at 3 mg/L inhibited P.donghaiense and all of its pigment concentrations almost not detected within the first day; The concentration of diadinoxanthin and diatoxanthin of C.decipiens increase significantly on the first day while the other pigments were not significant changed.The concentration of diadinoxanthin, diatoxanthin and fucoxanthin of P.parvum decreased to varying degrees with time while the remaining pigments were not affected by DEC at 3 mg/L.Except for zeaxanthin, concentrations of the other seven types of photosynthetic pigments in C.decipiens decreased significantly by DEC at 5 mg/L, A similar trend of the pigments concentration changes were also observed in P.parvum at the same DEC concentrations, in which except for zeaxanthin, seven types of pigments out of nine were significantly affected.