By optimizing the PI controller parameter tuning method of the motor that drives the grating, the positioning accuracy and stability of the servo motor were enhanced, and the line selection output of the single-path tunable TEA CO2 laser was improved and the tuning interval was shortened. The frequency domain model of the method of Permanent Magnet Synchronous Motor (PMSM) was deduced by the parameter. The analytical expression of the servo three-loop Proportional Integral (PI) was derived and set according to the actual requirements of the project. The PML40-530B8ANL AC direct drive motor and G-POLHOR10P100EE-E0 drive were used to build the optical path experimental device to verify the above parameters. The overshoot of the turntable positioning system is 4.86%, and the adjustment interval is 19.5 ms. Based on the turntable system, a fast-tuning TEA CO2 laser was built, and the laser weak line energy stability experiment was carried out during a tuning interval of 20 ms. The single pulse energy of the 9P(44) line is 74 mJ, the energy fluctuation range is ±3.35%, and the energy stability was increased by 3.62 times.