The invention relates to a data compression method for image comparison, an image comparison method and an apparatus. A data compression method comprises the following steps: a partitioning step of partitioning all eigenvalues by using a set threshold value and reserving eigenvalues not smaller than the threshold value; Sorting step of sorting the eigenvalues reserved in the previous step from large to small, and reserving the first N eigenvalues; The storing step of storing every X eigenvalues and their initial positions in the N eigenvalues obtained in the previous step through Y integer variables. By dividing and screening the eigenvalues, the eigenvalues and the initial positions are compressed and stored in integer variables, which greatly reduces the amount of the whole data, improves the processing speed, reduces the storage requirements, does not affect the contrast accuracy, and can adapt to the mass picture contrast processing of the entire Internet.