The invention relates to a voice encryption and decryption method for conversion parties on the basis of voice print, comprising the following steps of: (1) exchanging a section of shared secret by conversion parties; (2) starting the voice conversation by conversion parties, and determining a format of a network transmission packet; (3) in the process of conversion, calculating the MFCC (Mel Frequency Cepstral Coefficient) parameter of the voice characteristic information of self at certain interval by a voice sender, and extracting a secret key from the MFCC parameter; (4) numbering a voicepacket participating in calculating the MFCC parameter when the voice sender sends the voice packet; (5) receiving the voice packet by a voice receiver, and splicing the voice packet containing sequence numbers in order, calculating the MFCC parameter, and extracting the secret key from the MFCC parameter; (6) after the voice sender finishes sending the voice packet containing the vocal print secret key, sending a countdown voice packet at certain interval; and (7) after receiving the countdown voice packet, beginning countdown by the voice receiver, and replacing the current secret key when time is up, wherein both parties have symmetrical operation from steps (3) to (7). The voice encryption and decryption method generates the secret key by the voice characteristics of conversion parties, the length of the secret key can be chosen as required, and randomness is excellent.