In order to explore the suitable growth conditions and chlorophyll fluorescence parameters of two red algae Prorocentrum donghaiense and Skeletonema costatum,temperature(17,20,23,26 ℃) and light (40,80,120,160 μmol photons/(m²·s)),phosphate (0.1,1.0,5.0,10.0 μmol/L),initial biomass(1×10⁴,3×10⁴,5×10⁴,7×10⁴ cells/mL) , the algae culture experiment of the 4 factors with 4 levels was carried out. The results showed that the phosphate concentration (P<0.01) had the most significant effect on the peak chlorophyll a concentration of the two algae. And it was not significantly affected by light, temperature, and initial biomass. Phosphate addition experiment showed that in the low phosphate environment of 0.1 μmol/L and 1.0 μmol/L, the biomass and its stability of Prorocentrum donghaiense were higher than that of Skeletonema costatum. Prorocentrum donghaiense can survive after the high initial biomass depleting the phosphate, while the cell abundance of Skeletonema costatum declined continuously. In the environment of 5.0 and 10.0 μmol/L high phosphate, Skeletonema costatum proliferated faster and with higher biomass than Prorocentrum donghaiense.The fluorescence parameters F_v/F_m and α of Prorocentrum donghaiense were more stable than those of Skeletonema costatum, which showed the photosynthetic activity of Prorocentrum donghaiense was also stable.The smaller cell volume and larger specific surface area made Skeletonema costatum reach the peak value of biomass rapidly in the early stage of culture, which indicates that it has strong phosphate utilization ability. In the 10.0 μmol/L phosphate group, the four fluorescence parameters were the largest and the photosynthetic activity was the strongest, so it is necessary to prevent and control eutrophication.The photosynthetic activity of Prorocentrum donghaiense was more affected by light, and the photosynthetic activity of Skeletonema costatum was more affected by phosphate and light.