Abstract: Underwater installation of floating-body blocking gate was used in blocking and rehabilitation of the emergency overhaul gate slot at the bottom outlet No. 2 of Shuikou hydropower station. By modification and reuse of the original floating-body blocking gate, the overhaul at the bottom outlet No. 1 was successful. The gate blocked the water intake to create dry condition for construction and can be reused. This method was feasible, safe, reliable and cost-effective.