MFCC can express speech spectrum more accurately at low frequency, so MFCC is a good method to express the spectral envelope in voice conversion; A new and efficient algorithm for MFCC is proposed. At first, the staircase envelope is obtained through harmonic extraction, then the staircase envelope is transformed by Mel frequency scale, at last the MFCC coefficients are extracted by cosine transformation. The algorithm can be realized easily, and the result is good.