A multi-functional PH meter and the fabrication thereof are disclosed. The multi-functional pH meter immediately displays the measurement result on a liquid crystal display and saves in a compact flash card so as to provide portable functionality. In addition, the multi-functional pH meter has data communication functionality with a computer. Finally, the drift and hysteresis software calibration technique is applied. Thus, this method can increase ion detection accuracy and system reliability. The multi-functional pH meter includes a sensor unit, an analog signal processing unit, a microprocessor unit, the liquid crystal display unit, the compact flash card unit and a data transmission unit.