The invention provides a method and system for effectively estimating an input voice. The method comprises the following steps of: receiving input voice data; acquiring constraint conditions of rhythm of the input voice data; and providing an estimation result. The system comprises an input voice data receiving device, a rhythm constraint condition acquiring device, an estimating device and a result providing device. By adopting the method and system provided by the invention, the input voice data is not restricted, namely a user can read or read after the system according to specific character/voice and also can play freely.