A transmission control system for a hybrid-power driving system includes at least a gear shifting actuation module to control engagement of specific gearwheels and a clutch actuation module to control a clutch that couples an engine to the transmission. Gear shifts are required for each of the engine and the electric motor in the hybrid-power driving system. The control system minimizes power loss when a gear shift is occurring for the engine or the electric motor. By selectively controlling the clutch and engagement of specific gearwheels, power loss associated with a gear shift for one of these power sources can be directly offset by using the other power source.