The simple principle of Contact Image Sensor (CIS) and the noise types existed in CIS are introduced. The theory of suppressing these noise types for CIS by using Correlated Double Sampling(CDS) is described,and the timing relationship between driving signals CP/SP that CIS required and sampling-holding signals SH1/SH2 are also analyzed,these signals are produced by using Complex Programmable Logic Device(CPLD). CDS circuit principle is analyzed,and experiment of suppressing noise for CIS based on CDS is made. The experiment shows that satisfying results are obtained by using the technique of suppressing noise for CIS based on CDS.