A total of more than ten large-scale algal blooms occurred in the middle and lower reaches of the Hanjiang River during the winter and spring from 1992 to 2021, and the water ecological safety and drinking water safety were frequently threatened. Based on previous occurrences of algal blooms, the characteristics of algal blooms in the middle and lower reaches of the Hanjiang River and the causes of the outbreaks were analyzed and summarized. According to the response relationship between algal bloom and hydrological processes, the key indicators and their thresholds for algal bloom control were proposed. A joint ecological regulation scheme for water conservancy projects in the middle and lower reaches of the Hanjiang River was developed, and the ecological regulation mode and duration to suppress algal blooms were clarified. The control effect was analyzed based on the practice of ecological regulation for suppressing algal bloom in late January 2021. Studies have shown that the algal bloom events in the middle and lower reaches of the Hanjiang River is mainly occurred from January to March. After the construction of the Xinglong Reservoir, the section where algal blooms occurred has expanded from below the Qianjiang River section to the upper reaches of the Xinglong Reservoir area. As to the average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms, and there are differences in the threshold velocity (flow) in the Xinglong Reservoir area and Xiantao natural reach, the threshold levels are 0.20 m/s (1160 m³/s) and 0.67 m/s (1040-1200 m³/s), respectively. Finally, increasing release flow from the Danjiangkou Reservoir and fluctuating water levels of the Xinglong Reservoir are the key regulating method for algal bloom control, and the regulation duration is suitable for a period of 5 days.