Correlated double sampling is an indispensable processing technique for CCD signal conditioning. It can effectively reduce the reset noise. The double sampling clock phases are critical parameters determining correlected double sampling(CDS) technique′s effectiveness. To automatically determine the CDS clock phases, a pseudo-contrast based method was proposed. Through globally searching the maximum of the pseudo-contrast function by changing the signal sampling location and the reset sampling location in a fixed scene imaging set-up, the CDS clock phases could be determined automatically. Principle of the method was explained in detail. A test bench system was designed to verify the proposed methods. Experimental results show the effectiveness of the proposed method with an uncertainty about 3%, the robustness to different light intensities and better SNR performance compared to the conventional method.