ARL-1 Raman lidar system developed in Anhui Institute of Optics and Fine Mechanics was introduced for atmospheric CO2 measurements. It is based on third harmonic of Nd:YAG laser. This system emits laser beam at wavelength of 354.7 nm into atmosphere and collects Raman backscattering lights from atmospheric N[EQUATION] and CO[EQUATION] stimulated by laser beam. Mixing ratio profile of CO2 can be calculated with Raman backscattering signals of N[EQUATION] and CO2. In ARL-1 Raman lidar system, a setup for lidar constant calibration was designed. The experimental result shows that the stability of LED light intensity can reach up to 99.5%. Atmospheric CO2 measurements in planetary boundary layer were carried out with the Raman lidar system.