A method for the operation of a hybrid drive system is provided. The hybrid drive system has a first drive machine, for example an internal combustion engine, and a second drive machine, such as an electric machine. The hybrid drive system can also have a first gearshift sub-transmission and a second gearshift sub-transmission. The first gearshift sub-transmission can have a first input shaft that can be coupled to an output shaft using a first group of shifting gearwheel pairs, and the first input shaft can be coupled to the first drive machine. The second gearshift sub-transmission can have a second input shaft that is coupled to the output shaft using a second group of shifting gearwheel pairs, and the second input shaft can be connected with the second drive machine.