During a 1 m solar telescope tracking process, the relative change between the telescope optical axis and its auto-guiding system optical axis decreases tracking accuracy. According to the structure of the telescope optical, mechanical and electric control systems, the tracking error of auto guider caused by the change of optical axes is analyzed, and the detection method of the optical axes change is provided. The test results show that the maximum relative change of the optical axes is 46″. It varies only with the telescope altitude angles, independent of telescope azimuth angles. The major factor to cause the telescope optical axes change is telescope structure distortion under its gravity. The software correction model of the telescope optical axes which changes in the auto-guiding system is introduced to improve the long-term tracking accuracy decreased by the optical axes change.