With the continuous development and utilization of saline-alkali land, increasing quantities of saline-alkali water are being used for fisheries. However, the high pH value of the saline-alkali water environment is always a major factor restricting such aquaculture. Previous studies have revealed that the water environment pH value is mainly a result of the impact of CO₂ balance system (CO₃^2--HCO₃^--CO₂); the CO₂ balance system and activities of algae are also closely related. , two dominant microalgae species in saline-alkali aquaculture ponds, are of great importance in feed, nutrition and the aquaculture industry. Most studies have focused on the growth and reproduction of , and only a few have reported on their relationship to the pH value of the water environment. In this study, anorthogonal experiment was designed to study the effects of temperature (20℃, 25℃ and 30℃) and light intensity (2000 lx, 4000 lx and 6000 lx) on the regulation of environmental pH by the growth of . The results showed that temperature, light intensity and their interactions had a significant effects on the pH value of the algal medium, and there was a clear increase in pH during the exponential growth phase of these species. The water environment pH value of the medium generally increased by more than 9.50 as that alga grew under various temperature and light intensity conditions. The highest pH value of this medium was observed at 2000 lx and 25℃. Under these conditions, the water environment pH value of the medium reached its maximum value of 10.83 on the 9th day and the maximum algal density of 1.1×10⁷ cells/mL on the10th day. The highest pH value of the medium was observed at 6000 lx and 30℃. With the temperature and light intensity increasing, the maximum pH value and algal density were 7.73 and 8.0×10⁶ cells/mL, respectively, on the10th day. ANCOVA analysis showed a positive correlation between pH value and density of algae in the water environment. The correlation coefficient was 0.904; M. aeruginosa is much more likely to result in a higher pH water value than that of <0.01). Results also shows that a high pH value in the water environment can promote growth, which can promote a further increase in pH value. This is one of the main reasons for the high pH in aquaculture ponds, which always affects the healthy development of aquaculture. The results of this research can help in the regulation of water quality in aqua-culture ponds, avoiding higher water pH by algae control. Controlling the density of cells/mL can help to reduce the pH value of the water environment, and this is important for ensuring that water is suitable for the growth of culture organisms. These results can provide data to support the subsequent research and provide a reference for the future studies.