Abstract: In Conjugate-Structure Algebraic-Code Excited Linear-Prediction (CS-ACELP) algorithm, the algebraic codebook search calculation is through the nested loops. This leads the algorithm with a large computation, high computational complexity and time complexity. After thoroughly analyzing the reordering search sequence approach, this paper proposes a fast search method for fixed-codebook search based on modification of the search structure. In the proposed method, the combination of pulses obtained in the pre-search are directly used for the next full search. Therefore, the depth of nested loops in search is mitigated from 4 to 2. Compared with several other classic algorithms for fixed-codebook search, search times of the proposed method get a decreases of 30% to 98%. This method effectively reduces the computational complexity and time complexity, and codec sound quality is better G.729A.