In order to meet the need of the spaceborne CO2 lidar for the frequency stability of the seed light source, a set of frequency-stabilized laser was built based on the free-space body absorption cell combined with the frequency modulation spectroscopy technology.A set of frequency stabilization lasers were built through simulation and optimization of system design parameters. Studied the multi-beam interference noise was introduced by the volume absorption cell. By adjusting the modulation frequency to an integer multiple of the free spectral range of the interference fringe of the absorption cell, the influence of interference noise was suppressed, and the peak-to-peak value of the laser frequency jitter was about 150kHz, and the long-term frequency stability is lower than 1×10-11 at 10000s,which meets the application requirements of spaceborne lidar.