The invention relates to a color difference sorting method and system for solar cell pieces. The method comprises the following steps that (1), a plurality of sample solar cell pieces are taken, the color difference sorting value of each sample solar cell piece is obtained through calculation and stored into a database, grading numbers of the solar cell pieces and the color difference sorting value range corresponding to each grade are determined; and (2), solar cell pieces to be sorted are taken, color difference sorting values of the solar cell pieces to be sorted are obtained through calculation, and the grades of the solar cell pieces to be sorted are determined according to the color difference sorting values of the solar cell pieces to be sorted and the color difference sorting valueranges obtained in the step (1), wherein the color difference sorting values are calculated through the following steps that (10), color images of the solar cell pieces are obtained; (20), graying processing is carried out on the color images, and gray level histograms and average gray values of the three channels of R, G and B are obtained respectively; and (30), weighting summation is carried out on the average gray values of the three channels, and color difference sorting values are obtained through calculation.