In natural environments, factors such as dam discharge, algal photosynthesis, and rapid increases in water temperature can lead to dissolved oxygen (DO) or total dissolved gas (TDG) supersaturation, potentially causing gas bubble disease or mortality in fish. To quantitatively evaluate the contribution of algal photosynthesis to dissolved gas supersaturation, this study employed the light-dark bottle method in the Xiangjiaba Reservoir area. Additionally, the relationship between dissolved gas saturation and algal density was analyzed downstream in the Jinsha River, accounting for the combined effects of dam discharge and algal photosynthetic oxygen production. Results indicated that algal oxygen production increased TDG saturation by 0.18% to 5.67%, an effect substantially smaller than that induced by spillway discharge. The impact of algal photosynthesis on dissolved gases was strongly influenced by hydrodynamic conditions. In tributaries, both DO and TDG saturation showed a significant positive correlation with algal density, whereas this correlation was negligible in the mainstream. The impact of algal photosynthesis on DO saturation is greater than on TDG saturation.The findings of this study provide scientific basis and technical support for understanding the relationship between dissolved gas supersaturation and algae, as well as for regulating dissolved gas supersaturation.