A truncated differential-linear cryptanalysis method is proposed, which extends differential-linear method. DES (data encryption standard) algorithms of 9-ro und and 11-round were analyzed. The method was proved more convenient and widel y applicable. In DES like cipher algorithms, the fact that the order in which S -boxes were placed would affect the security of cipher was shown by the method. In this way, the truncated differential-linear method gives a criterion for or dering S-boxes optimally.