A method using rotating Fabry–Perot (FP) mirror to measure CO2 laser wavelength was developed. The variation of FP transmittance changing with laser incident angle was calculated theoretically and the variation curve was given. The calculation illustrates that the variation of FP reflectance with incident angle 0 to 30 deg has little effect on the transmittance of FP. In the experiments, the CO2 laser transmittance variation of FP was measured at a wavelength of 9.27 μm. To improve the measurement precision of the laser wavelength, the method using the centrosymmetric peaks of FP transmittance curve in the range from −20 to +20 deg of laser incident angle was proposed. The precision of the measurement is about 0.01 μm. The experiment result is consistent with theoretical analysis, which demonstrates the feasibility of the laser wavelength measurement using rotating FP method.