Abstract: The paper investigates the capability of extension of characteristic waveform interpolation(CWI) algorithm to wideband speech coding.The analysis of wideband characteristic waveform sequences shows that using classical CWI algorithm directly is not suitable for enhancing the wideband coding efficiency and affects the computational complexity.The paper introduces bandwidth expansion(BWE) technique to process the high frequency band.High and low frequency bands were recovered separately by CWI and BWE algorithms.The final 5.15?kbit/s low bit rate wideband coder can enhance the trueness of speech,the discriminability of consonants and the recognizability of the speaker.The coding result is close to that of AMR-WB 6.6?kbit/s.