The invention discloses a method for judging the similarity of pictures subjected to non-equal-ratio stretching. The method comprises the steps of 1, dividing a source picture into M N*N matrixes; 2,performing comparative stretching or zooming on a comparison picture and the source picture: A'=(the transverse pixel source picture/the transverse pixel comparison picture), and A,B'=(the longitudinal pixel source picture/the longitudinal pixel comparison picture)B; 3, dividing the converted comparison picture into M N*N matrixes; 4, performing assignment of values (which are 0, 1......N-1 in sequence) on elements of all the N*N matrixes of the source picture and the converted comparison picture according to the grey levels from low to high, wherein 0 represents a white color and N-1 represents a black color; 5, according to the sequence, comparing element grey values in M and M' to obtain similar ratios of M and M'; and 6, according to the similar ratios obtained in the step 5, performing calculation to obtain the similarity between the source picture and the comparison picture.