Techniques for simultaneously and efficiently eliminating echo and noise mixed in voice are disclosed. According to one aspect of the present invention, an adaptive filter system for eliminating noises and echo mixed in voice signal comprises a first signal adaptive filter, a first subtractor, a second adaptive filter and a second subtractor. The first signal adaptive filter estimates the noise mixed in the voice signal according to a reference noise. The first subtractor subtracts the noise estimated by the first adaptive filter from the voice signal to obtain a voice signal without the mixed noise. The second adaptive filter estimates the echo mixed in the voice signal according to a remote voice signal. The second subtractor subtracts the echo estimated by the second adaptive filter from the voice signal without mixed noise to obtain a clean voice signal.