Abstract: In speech coding algorithms,the Mixed Excitation Linear Prediction (MELP) algorithm can do better to imitate the natural speech characteristic and can synthesize a high quality speech in the low bit rate,so it becomes one of the most potential algorithms in the modern low bit rate speech coding. In the wireless communication,satellite communication,the military and secure communication,the channel bandwidth is a serious problem,so it is necessary to study the compressed (even very low bit rate) speech coding technique. This paper analyses several low bit rate speech coding algorithms based on MELP,summarizes the theories and the key techniques,and finally makes a comparison of the speech qualities.