The invention provides a DES (Data Encryption Standard) encryption method and device. The method comprises a step of performing n rounds of S box function processing, wherein n S box functions corresponding to the n rounds of S box function processing comprise that the ith round of S box function is Si(x)=S(x E(X((i-1)mod k))) P(-1)(X(I mod k) X((i-2)mod k)),wherein i is greater than or equal to 1 and is smaller than or equal to n; k is a natural number; i is a positive integer; x is an input value of the S box function; X(0) to X(x-1) are k first random number masks; E is an extended permutation function; P (-1) is an inverse permutation function of the permutation function P. According to the method and the device, the safety of data can be improved.