A new method is proposed for direct wave and wall clutter suppression in through-wall surveillance using spread spectrum radar. The impacts made by different analog to digital converters (ADC) and noises on the results of this method are analyzed. Synthetic aperture radar (SAR) imaging of stationary targets behind a wall is taken as an example to demonstrate the effectiveness of the method. It is seen that the direct wave and wall clutters can be mitigated significantly and the target information can be enhanced greatly. The clutter suppression method is insensitive to the sampling rate and bit of ADCs, therefore a low-cost ADC could work with no sacrificing on system performance. Numerical results also show that the method could tolerate a noise level as high as 4dB.