A Raman lidar was developed for atmospheric CO2 measurements in the low troposphere in Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. Combined with real atmospheric condition, atmospheric CO2 uncertainty was analyzed using the Raman lidar measurement cases and observation results by CO2 analyzer. Analyzed results show that the lidar reveals fine stability and higher accuracy. For example, it’s uncertainty can be limited within 1.2 ppm up to 1km altitude and 2.5 ppm up to 2 km altitude under good weather condition.