A scan signal compensating method and a scan signal compensating device based on a scan driving circuit are provided. The method exemplary includes: acquiring a scan signal compensation voltage value in a detecting period; adjusting a clock signal(s) and a DC voltage source(s) inputted to the gate driving circuit according to the scan signal compensation voltage value, in an adjusting period. In particular, after the scan signal compensation voltage value is obtained, amplitudes of the clock signal(s) and the DC voltage source(s) inputted into the gate driving circuit are adjusted, thereby solving problems of ghost and flicker of a display device caused by pixel capacitance leakage in the active area resulting from the drift of I-V characteristic curve of TFTs in the active area suffered from a long-term voltage difference.