Abstract: Given a finite subset　Wand a vector x both in k-dimension space R\+k,the method to fast locate the vector in W closest to x is of great value in various applications,and would speed up the encoding for vector quantization and the iterative process of generating codebook based on SOFM algorithm. This paper analyzes the properties of SOFM algorithm and the existed fast encoding algorithms,and presents a new method to speed up the codebook generating. The advantages of the new method are in high searching efficiency and less memory requirement. The experiment shows that the running time of the new algorithm is only about 42% of the existing one's. The new algorithm proposed in this paper is of applied value in many fields such as pattern recognition and computer graphics.