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This paper described the principle of the direct vector quantization (DVQ) algorithm which was applied to simulated decoder module and codebook search module in LD-CELP speech coding algorithm. The synthesis filter in simulated decoder module was replaced by the inverse-perceptual weighting filter, removing the operation of impulse response h(n) in the codebook search module. The result showed that the DVQ algorithm decreased calculation quantity and improved the efficiency of codebook search. The multiplication operation amount of energy calculator and time-reversed convolution module could be reduced by 75%, and the addition operation amount could be reduced by 77.78% in an adaptation cycle of four vectors (20 samples), while SNR was equivalent to that of LD-CELP and speech quality had not almost change.