An automatic operation method for setting temperature compensation coefficients of a digital pressure gauge is revealed. Primarily, a microcontroller unit (MCU) in the pressure gauge is equipped with built-in calibration procedures. The gauge is placed into a temperature-controlled chamber in order to obtain the temperature coefficient of offset (Tco) and temperature coefficient of span (Tcs). This method is the automatic measuring outputs of zero pressure/full scale at two temperatures to calculate the temperature coefficients Tco/Tcs. The two temperature compensation coefficients are stored in the MCU inside the pressure gauge. As the pressure gauge operates in any working temperature environments, the gauge based on a certain algorithm formula with the two stored temperature coefficients shows an accurate pressure reading.