The study focuses on a test and discussion of non-dispersive infrared CO_2 flask sample analysis and standard gas calibration system developed by NOAA/CMDL and used in the baseline atmosphere monitoring in China with the mixing ratios of carbon dioxide in the flask air samples tentatively taken at Waliguan(Qinghai), Linan(Zhejiang),Longfengshan(Heilongjian) and Shangdianzi(Beijing) being measured.Meanwhile,a comparison was made with the continuous online measurements at Waliguan.The results all indicate that the system is of high-level sensitivity,precision and stability with an automatic function from sample injection to data processing.It can be applied to the calibration of CO_2 standard gases and the analysis of flask samples,being easy-operating and reliable.The air sampling and analyzing system can be used,to some extent,instead of the in-situ continuously monitoring system.It is also an economical and practical way to take samples in different sites and analyze together