Abstract: To strengthen the water safety guarantee of Danjiangkou Reservoir, with the data of algal monitoring in the reservoir from Jul. to Oct. in 2025, the concentration variation characteristics and causes of 2-MIB in Danjiangkou Reservoir were analyzed. the paper shows that: (1)There is a significant synchronization between 2-MIB and AD in Danjiangkou Reservoir in terms of temporal variation. During the peak period of algal proliferation (August-September), both reached obvious peaks. The peak 2-MIB concentration was nearly 30ng/L in the center of the Dan Reservoir, nearly 45ng/L at 0+900m downstream of the dam, nearly 35ng/L at Taicha Regional Boundary Station, and nearly 25ng/L at Liangshuihe-Taizishan. AD showed a similar spatial gradient.(2)The distribution of 2-MIB is jointly driven by "water quality-biological factors from direct algal metabolism" and "basic factors of nutrients-habitat". 2-MIB is highly correlated with factors such as algae, water temperature, pH, organic matter, and nutrients, among which the correlations with Chla, TN, WT, pH and EC are particularly significant.