The invention provides a decoding device and method. The method is suitable for the condition that periodic repeated code elements exist in original information code elements. The method comprises the steps that scrambled information code elements k0, k1, k2,..., kt-1, kt,..., km-1 with the length of m, the initial state M (0) of a
long code generator and a
state transition matrix B are received; constructing auxiliary data k0 ', k1', k2 ',..., k' 82 according to the scrambled information code elements k0, k1, k2,..., kt-1, kt,..., km-1; wherein ki '= ki + kt-1 + i, and i = 0, 1,..., 82; according to the auxiliary data k0 ', k1', k2 ',..., k' 82, the initial state M (0) and the
state transition matrix B, a 42 * 42 full-rank matrix D is obtained through calculation; wherein the first behavior of the D is CBn, and then a scrambling code # imgabs0 # with the length of m is obtained through sequential analysis, the scrambling code obtained through analysis and scrambled information code elements k0, k1, k2,..., km-1 are subjected to modulo 2 addition operation, and an original information code element with the length of m is obtained.