Abstract: In the conventional Doppler ultrasound instruments,a high-pass filter is usually used to remove the wall clutter signal.However,the low-velocity blood signal is also removed.To over-come this limit,recently proposed methods based on the spline reconstruction,the principle com-ponent analysis,the adaptive filtering and the wavelet transform are firstly presented.Computer simulation experiments are done to compare these methods′ performance.The result shows that methods incorporating the spline reconstruction and the adaptive filtering perform better than the rest ones.They remove the wall clutter signal without considerable loss of low-velocity blood signals and may be regarded as effective methods in the separation of the wall clutter and Doppler blood signals.