The invention provides an adjusting system of a hydropower station for improving the power adjusting speed and adjusting precision by closed-loop power adjustment. The adjusting system comprises a monitoring system, a control unit and a speed adjuster; the adjusting system uses a power adjusting function of a speed adjuster system; in consideration of using the speed adjuster as a direct acting mechanism for unit power adjustment, the adjusting response speed and the adjusting precision are both better than the monitoring adjustment, so that the speed adjuster is operated by a power mode; the load setting is sent to the speed adjuster through a mold outlet mode by a monitoring LCU to form a power closed loop on the speed adjuster; the speed adjuster finishes the unit power adjustment to eliminate the defect of out-of-limit power or insufficient adjusting quantity caused by different water heads in primary frequency modulation acting period; and the power closed-loop adjustment of the speed adjuster prevents multi-conversion of adjusting instructions in the monitoring closed-loop adjustment, improves the power adjusting speed and adjusting precision, prevents assessment due to the factor that the adjusting speed dose not meet the power grid requirements, and improves the enterprise power generation efficiency.