Abstract: In order to understand the role of the temperature and the concentration of N and P in the growth of Merismopedia and Scenedesmus, we carried out the monoculture and co-culture of Merismopedia and Scenedesmus using BG11 medium in this study. Nutrients at different concentrations were added into the medium and the subjects were cultured at different temperatures. In the monoculture system, Merismopedia stopped growing at the test temperatures when the concentration of TP was 0.1 mg/L and 0.5 mg/L, but the growth was normal when the concentration of TP was 1.0 mg/L and 1.5 mg/L. The optimal temperature for the cell growth was 25℃, followed by 35℃ and 18℃ with TP at various concentrations. The cell density of Scenedesmus became higher along with the increase in the concentration of nutrients in the monoculture system, and the optimal temperature for the cell grew was 18℃, followed by 25℃ and 35℃ with TP at various concentrations. In the co-culture system, Merismopedia had little effect on Scenedesmus under most conditions, except that the competition ability of Scenedesmus was stronger than that of Merismopedia when the concentration of TP was 1.5 mg/L at 35℃. Merismopedia was seriously affected by Scenedesmus, and it was suppressed under most conditions but was promoted when the concentration of TP was 0.5 mg/L.