A signal correcting method and a circuit thereof are provided. In the method, first, the values of a plurality of input signals are clamped to generate a plurality of corresponding clamping signals according to a plurality of adjustable predetermined values. Then, a combined multiplication operation is performed to the clamping signals according to the coefficients in a matrix obtained by multiplying the coefficients in at least two predetermined correcting matrixes, so as to output a plurality of results. Next, the results are respectively clamped according to a plurality of corresponding predetermined thresholds so as to output the corrected input signals.