The gear transmission is widely used in mechanical engineering. During the work time, the size of the bearing hole has changed due to temperature increase, leading to the size, shape and position tolerances of shaft and bearing with the components deviates from the original design requirements, thus making the spatial location of axis , gear with the gap and tooth contact angle changed, noise increasing, gear life shorten. In this paper, the thermal deformation experiments of the commonly used mechanical engineering machinery bearing hole has been carrying on. Using self-developed experimental device, in the -10 ~ 80°C temperature range, a single hole is measured accurately on the different radial direct, and measurement data is analyzed, combined with the structure and size of surrounding of hole. The results of theory and test analysis show that the thermal deformation feature of hole is not only closely related to the physical attributes of material, but still affected by its own structure and size of parts. That means thermal deformation of parts has non-similar thermal deformation features.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.