In this paper, the Error Motion in ISO 230-7:2015 is introduced to evaluate the radial rotation accuracy for the gas dynamic gyro motor. A measurement system of rotation accuracy is built up based on 3-points error separation method. The roundness error, eccentricity error of installation and motion error are separated, respectively. In addition, a method to measure the radial centrifugal deformation and thermal deformation is proposed. Finally, the experiment system is set up and the validity of separation accuracy is verified, which provides the basis for the quantitative evaluation of gyro motor rotation accuracy in production process.