Abstract: A method for generating a random code book having a characteristic similar to a periodic component of voice in code-excited linear predictive (CELP) coding. The method includes generating an adaptive code book that removes the periodic component of a current subframe of a speech signal. An adaptive code book array is generated with respect to the current subframe on the basis of an optimal delay and gain obtained in generating the adaptive code book. A number of code word arrays are generated from the adaptive code book array and the excited signal of the immediately previous subframe. A code word that has the maximum value is selected from each code word array generated in the code word array generating step. Each code word array is normalized using the selected code word. The normalized maximum value in each code word array is selected and scaled by the power of the most previous frame. A random code book including a set of the scaled selected maximum values is generated.