The tunable waveguide RF-excited CO2 laser is developed. Hooting modes are suppressed by optimization of the optical scheme of a waveguide cavity. The laser radiated at more than 70 lines with output of 0.3-3 W in single-mode and single-frequency regime. On the basis of two such lasers, the two-channel CO2 laser system controlled by computer is developed, that is intended to operate in mobile heterodyne differential absorption lidar (DIAL). The laser frequencies can be stabilized at the centers of lines or synchronized with required frequency interval. The laser system was tested under field conditions in mobile heterodyne differential absorption lidar and has shown satisfactory results. The developed laser system can be used as a stabilized double-frequency source of radiation in trace gas analyzer with direct detection.