Based on laser atmosphere backscattering spectrum, the design and experiment of a Raman lidar system for measurement of atmospheric CO2 are presented. 354.7nm third harmonic of Nd∶YAG laser is transmitted with 350mJ pulse energy and repetition rate of 20Hz. The receiver employs a photomultiplier tube with quantum efficiency of 25% and 200MHz photon counter, and it detects Raman backscattering 371.66nm(shift 1285cm-1) signal. At 1h integration, the signal to noise ratio below 2.5km is greater than 8. Combinatorial filter is used to reject interference presented by 354.7nm intense Mie-Rayleigh backscattering and 375.4nm Raman backscattering from O2. We compare the Raman return signal at 371.66nm from atmospheric CO2 with the reference Raman return signal at 386.7nm from atmospheric N2 to retrieve the atmospheric CO2 concentration.