Abstract: A software of thermal analysis，Icepak，is used to calculate the heat exchange in enclosing channels of LAMOST.The effect of the thermal radiation and conduction of the enclosed wall surface on the whole temperature field is emphatically analyzed.Based on the cooling scheme of ventilating duct, the models of the thermal radiation and conduction are set up respectively, and the heattransfer structure on the walls in the dome is described with them. The temperature filed distribution of the main optical assembly (focal surface) is calculated with a simulation method when the thermal radiation and conduction on the wall surface are increased, and the calcution results are compared and analyzed.The numerical calculation and simulation results show that the effect of the wall surface heat transfer on its internal temperature field is not serious, the cooling shcheme of ventilating duct can control the maximal temperature gradient on the focal surface within 0.4℃/m successfully and the characteristic structure of enclosed wall is effective on the heat transfer. The conventional cooling project is still powerful with the new structure of the walls. The thermal analysis and simulation are helpful to the theoretical study on the seeing and the design of the LAMOST dome.