The design and experiment of a Raman lidar system for measurement of atmospheric CO₂ are presented. 354.7 nm third harmonic of Nd∶YAG laser is transmitted with 60 mJ pulse energy and repetition rate of 20 Hz．Receiver employed photomultiplier tube with quantum efficiency of 25% and 200 MHz photon counter,and it detects Raman backscattering signal 371.66 nm(shift 1285 cm^－1)from CO₂. Combinatorial filter is used to reject interference presented by 354.7 nm intense Mie-Rayleigh backscattering and 375.4 nm Raman backscattering from O₂。Other wavelength radiation was excluded to enter photomultiplier tub. The interference from O₂ is approximately 1% of the anticipated CO₂ signal.