Abstract: Traditional single mode speech coding designed under some assumed worst case conditions would waste system capacity under the good condition because of the complex wireless environment. Based on the adaptive multirate (AMR) speech codec, standardized by ETSI, the general AMR concept was reviewed, the architectural diagram was analyzed and its performance was simulated on GSM platform under three typical environments with Chinese language. The simulation shows the synthetic speech quality of AMR is 0 5 to 1 2 MOS higher than that of other coding mode in whole work range.