Abstract: In this paper, foe Authors study the characteristics of CO₂ anomalies in 0.5m and 2.0m depth in Tangshan and Xiadian buried active faults and Xianhe-Huangzhuang buried inact ive fault in the northern part of North China, and preliminarily discuss the mechanism of CO, anomaly and applications of CO₂ anomalous features in different depths in determining locations and activities of the buried faults. CO₂, contents in 0.5m depth show distinct anomalies both in the buried active and inactive faults, however, CO₂ contents in 2.0m depth show notable anomalies in the buried active faults but don't show anomaly in the buried inactive fault. The width of CO₂ anomaly estension in 2.0m depth is much more narrower than that in 0.5m depth. It is suggested that CO₂ in 0.5m depth is mainly originated from biogenic agency while CO₂ in 2.0m depth is primarily derived from degassing in the processes of carbonte rock ruptures caused by fault movement.