In-situ custom-designed gas chromatography(GC)-HgO system was established for the continuous measurement of atmospheric CO at Waliguan Baseline Station(36 degrees 17' N, 100 degrees 54' E, 3816 m asl) in western China. The system's assembling, testing, running and calibration indicated that the chromatographic method has stable baseline and high separation efficiency, as well as reliable detection method. This system adopted high automatic operating techniques and followed strict quality control. It is up to the standard of WMO's baseline watch on global atmosphere. According to the flask sampling results of in-situ CO variation at Waliguan, CO standards in clean dry air under international comparison were used to determine the adjustable working standard curves, so as to calculate the ambient CO mixing ratios based on peak height. This system's detection limit for CO is around 1 x 10(-9) (V/V), the precision is below 0.1% and accuracy in +/- 0.05%, it can provide continuous and accurate surface CO mixing ratios in baseline areas of China.