The invention discloses an active power output control parameter pre-processing method for a hydropower station during automatic power generation. The method involves an automatic generation control (AGC) functional block, a proportion integration differentiation (PID) functional block and a pre-processing functional block, and a device parameter and a dynamic parameter are directly input or processed by the pre-processing functional block and then are sent to the AGC functional block and the PID functional block for updating. An active power set value of a single machine of each power generation set can be calculated according to a full-station active power target value of the hydropower station, PID closed-loop adjustment is carried out on the active power actual value of the single machine, and the running requirements of the power generation seat evading from a vibration region and one-time frequency adjustment of the hydropower station are met; and a pre-built mode of inputting a combination output model of an AGC machine set is adopted, data conversion existing in a machine set form is data in a power station form, the solution efficiency is improved, and the automatic active power output control demands of different large- and medium-size hydropower stations with multiple vibration regions and multiple types of machines sets can be met.