A pixel data preprocessing method includes the steps of: inputting a first frame data into a timing controller; performing a differential operation on the first frame data to generate a first frame differential data; writing the first frame differential data into a frame memory with the timing controller; reading a second frame differential data from the frame memory with the timing controller; performing an inverse differential operation on the second frame differential data to generate a second frame data; comparing the first frame data and the second frame data; and outputting a driving data with the timing controller according to a comparison result of comparing the first frame data and the second frame data. The present invention further provides a pixel data preprocessing circuit.