A hydraulic control device for a hybrid transmission is designed such that the cooling and lubrication oil line of the system are in oil communication even before the main oil line pressure reaches the set pressure of the overflow valve, so as to lubricate the transmission as soon as possible. The hybrid transmission design further provides an overpressure protection for the cooler. The hybrid transmission further uses a proportional pressure reducing valve to control the lock-up clutch, thus making for the improvement of its braking performance.