Abstract: In order to reduce the environmental hazards of ducks-wastewater and decrease the cost of largescale cultivation of microalgae, Scenedesmus dimorphus was used for treatment of ducks- wastewater to investigate the effects of different pH, inoculation amount and concentration of indole acetic acid on the biomass production rate of Scenedesmus dimorphus. On the basis of single factor experiments, the culture conditions of Scenedesmus dimorphus in ducks-wastewater were optimized by response surface method. The results indicated that: Scenedesmus dimorphus had a good processing capacity on ducks- wastewater, the removal rate of total nitrogen, total phosphorus, ammonia nitrogen reached 79.27% , 83.27% and 88.37% , respectively. The optimal culture conditions were determined 8.8 of pH value, 30.63% of inoculation and 0.60 mg/L of indole acetic acid, and a high biomass production rate of 0.0723 g/(L·d) was obtained. The results suggested that ducks-wastewater was a promising feedstock for production of microalgae.