A frequency selecting module for a touch system includes a storage unit, for storing a sum of at least one of a plurality of sensing signals of a plurality sensing channels in the touch system; a spectrum calculating unit, for transforming the sum of the at least one of the plurality of sensing signals stored in the storage unit to generate a spectrum data and storing the spectrum data to the storage unit; and a selecting unit, for generating an adjusting signal according to the spectrum data to select one of a plurality of operation frequencies as a working frequency of the plurality of sensing signals.