The principle of the grating tuning is introduced, the performance of the blazed grating is analyzed and the grating parameters are selected. The system of the grating tuning line selection of TEA CO2 laser is designed, the hardware and software of the tuning line selection output control system are developed. The experiment shows that the system of the grating tuning line selection of TEA CO2 laser can accurately and fast realize the output of the grating line selection.