Abstract: This paper presents an analysis on active power fluctuations in the grid connection experiment of the Jinping-I generating units, focusing on two causes of the fluctuations. The major cause was that in the cases of low water head, the adjustment parameter of local control unit (LCU) in the monitoring and control system was unable to be adapted to the active power regulation time of the turbine that became longer. Our analysis also revealed the other cause: the load-up operation was superimposed in phase on the second overshoot correction in the previous adjustment. Besides, water hammer could possibly play a role in this operation. Thus we suggest the following methods to solve the fluctuation problem. First, a manual interface for plus-or-minus operation of guide vane opening should be added to the computer monitoring and control system including the corresponding software. Second, the governor must be ensured to run in power feedback mode. Finally, the LCU should have an automatic function of changing its proportion integral derivative (PID) parameter and turn off its close-loop active power regulation in the cases of low water head operation.