Abstract: To reduce the computational complexity of characteristic waveform(CW) representation and alignment, improved algorithms for CW representation and CW alignment are proposed in this paper by applying Fast Fourier Transform, cubic B-spline interpolation and period extension. The improved algorithms are correspondingly independent, and their comploxity is reduced from 43.252 million operations per second to 9.178 million operations per second. The experimental results show that the improved algorithms have greatly reduced the computational complexity and kept the same speech quality as original coder.