A liquid detecting method and controller for a capacitive touch pad are disclosed. The method includes performing a first mutual capacitance measurement of sensing points of the capacitive touch pad to obtain multiple first sensing values, and then performing a second mutual capacitance measurement of the sensing points to obtain multiple second sensing values, wherein the first and the second mutual capacitance measurements using different frequency of driving signals or different sensing periods for sensing the multiple sensing points. According to the multiple first sensing values and the second sensing values, whether there is liquid on the capacitive touch pad can be determined.