An overdrive system adaptable for a dynamic gamma generator is disclosed. A current gray-to-voltage converter (G/V) converts image data of a current frame from gray code to voltage level, and a previous gray-to-voltage converter (G/V) converts image data of a previous frame from gray code to voltage level. The voltage level of current frame and the voltage level of previous frame are inputted to an overdrive-voltage lookup table to retrieve an overdrive voltage level. Afterwards, a voltage-to-gray converter (V/G) converts the retrieved overdrive voltage level from voltage level back to gray code, resulting in an overdrive gray code. Accordingly, the overdrive gray code is compensated. Alternatively, the overdrive gray code is used to update an overdrive-gray-code lookup table, an output gray code of which is fed to the source driver.