A method of transforming a serial scrambler to a parallel scrambler, a parallel scrambler and a double-edge-triggered register with XOR operation are provided. The method transforms a serial scrambler to a parallel scrambler according to a characteristic polynomial:.function..times..times..times..times..times..times..function.- .times..times..function. ##EQU00001## The method first determines a transformation formula:.function..times..times..function..times..function. ##EQU00002## according to the parameters of the characteristic polynomial. The parallel bits B.sub.j=[b.sub.Mj, b.sub.Mj+1, . . . , b.sub.Mj+M-2, b.sub.Mj+M-1] are arranged in order. The transformation number R=2.sup.t (the initial number of t is 0) is set. The parallel bits are replaced by the transformation formula. When (k-R)N+i+R(N-q) is larger than Mj-1 in the transformation formula, 1 is added to t in the transformation formula R=2.sup.t and the transformation formula is re-counted. Finally, the XOR gates are connected to the registers according to a computed result from the transformation formula.