Aiming at the adaptability problem of common optical path system to ambient temperature, a regional thermal control method of primary mirror assembly based on comprehensive heat transfer was proposed on the basis of the temperature-optics deformation characteristics. The heat transfer model of the primary mirror assembly was established, and the temperature distribution properties under typical conditions were analyzed. The thermal simulation of the primary mirror with different materials was carried out, and the model was modified with the thermal optical test results, so that the absolute deviation between the simulation and the measured results of the temperature field was less than 1.4 ℃. At the same time, the temperature gradient control threshold of the primary mirror assembly was determined. On this basis, the regional heat transfer strategy was adopted to make the primary mirror assembly reach the thermal control goal of high temperature rise level and low temperature gradient. Taking a primary mirror assembly as the object, the simulation and test were carried out. The results show that when the average temperature rise of the primary mirror reaches more than 16 ℃, the axial temperature gradient of the mirror is equal or lesser than 2.5 ℃, the radial and circumferential temperature gradient is equal or lesser than 2.4 ℃, and the variation of the primary mirror shape is less than 0.005 λ, which can provide an optimization idea for the overall thermal control design of the common optical path system.