Abstract: To investigate the toxicological effects of DEHP on Scenedesmus acuminatus, a green algae isolated from Han River, chlorophyll fluorescence induction kinetics curve and the parameters and antioxidatant system were utilized. The results indicated that DEHP significantly decreased SOD activity but increased MDA content in a concentration and treatment time-dependent pattern, and that DEHP increased Chlorophyll contents at low concentration. Chlorophyll fluorescence induction kinetics curve and the parameters analysis showed that 10 mg/L DEHP promoted deoxidation of QA- in the electron transport chain, and 100 mg/L DEHP reduced the deoxidation of QA-. DEHP decreased Fv/Fm with the increased concentration and the duration time. The results revealed that DEHP has an obvious damage on the photosynthetic system and antioxidant system of S. acuminatus, and fast chlorophyll fluorescence induction kinetics (OJIP-test) can be effectively used to detect detrimental damage.