It is necessary for us to enhance the security service on smart phone by using voice data on authentication procedure. In this study, a voice data based one-time password generation mechanism is designed and implemented for enhancing user authentication on smart phone. After receiving a PIN value from the server, a user inputs his/her own voice biometric data using mike device on smart phone. And then this captured a voice biometric data will be used to generate one-time token on server side after verification procedures. Based on those mutual authentication steps, a voice data based one-time password(V-OTP) will be generated by client module after receiving the one-time token from the server finally. Using proposed voice one-time password mechanism, it is possible for us to provide more secure user authentication service on smart phone.