Quality of transmission is very important in digital communication. The BER (bit error rate) of a PCM encoding method may be varied according to different working condition or different signal source. Theoretically, the BER of encoding method can be estimated mathematically. The BER is generally assumed as a constant value. The BER, however, is not deterministic in real world. In this paper, a Dynamic PCM Selector that can dynamically select an optimal PCM codec module is proposed. The system can dynamically switch to the encoding mode with possible lowest BER, according to the current type of the transmission. By way of this design, it can greatly reduce the overheads of the error correction process.