In a method for controlling a lock-up hydraulic pressure in an automatic transmission, which controls said hydraulic pressure in accordance with a hydraulic pressure control time schedule to be provided to a lock-up clutch that mechanically connects and disconnects a pump impeller of a torque converter of said automatic transmission connected to an engine and a turbine runner connected to transmission gears during a gear shifting operation,
- the improvement comprising the steps of detecting engine speeds, determining the difference between the detected engine speeds and reference engine resetting said hydraulic pressure control time schedule to have higher pressures than the former pressures if a difference between detected engine speeds and reference engine speeds exceeds a certain given limit
- and controlling said hydraulic pressure for subsequent shift operations in accordance with the resulting reset hydraulic pressure control time schedule.