To analyze the temperature deformation of photo-electronic theodolite mechanical structure, the entity model of theodolite mechanical structure was established, and stable-state thermal analysis of mechanical structure was done by using the software Ansys/Workbench. Moreover, the temperature distribution of mechanical structure, temperaturedeformation of mechanical structure and the temperature deformation of mechanical structure along Z direction were given. The analysis shows that part of the mechanical structure has a greater deformation under the conditions of thermal inhomogeneity and temperature changes. At 27.938℃, the maximum deformation of mechanical structure is 0.133 mm, the deformation of columns causes horizontal axis inclined 2.8″, and deformation reduces pointing accuracy of theodolite. The analysis provides reference information for structure optimization design, distribution of temperature sensor and local temperature control of photo-electronic theodolite.