This paper presents a simple but high performance architecture for multi-channel analog-to-digital conversion. Based on compressive sensing, only one SAR ADC is needed to convert multi-channel sparse inputs, leading to significant analog power saving and hardware saving. Moreover, it helps avoid problems occurring in conventional multi-channel ADCs such as timing skew, offset mismatch, and gain mismatch. A 12-bit SAR ADC converting 4-channel sparse signals simultaneously is designed in 130nm CMOS process. The design reaches a SNDR of 66.3dB and consumes an average power of 58μW at the sampling frequency of 1MHz. The L1 minimization method is chosen to reconstruct the input signals. The single-tone and multi-tone inputs can be reconstructed with a minimum precision of 68dB and 55dB THD, respectively.