A calibration method for a capacitance level sensing apparatus (10) is applied for a tank measurement. A measurement signal generating circuit (102) generates a measurement signal (104) to proceed with the tank measurement. According to a measurement result measured through the measurement signal (104), a sensing circuit (108) transmits a sensing signal (110) to a control unit (112). According to the sensing signal (110), the control unit (112) determines whether the sensing signal (110) is in an effective range or not. If the sensing signal (110) is in the effective range, the control unit (112) sets a total capacitance in accordance with the sensing signal (110) as a measurement base value. If the sensing signal (110) is not in the effective range, the control unit (112) controls the measurement signal generating circuit (102) to adjust a measurement frequency of the measurement signal (104).