The plasma melting furnace is an important device for radioactive waste plasma melting treatment technology, and its overall furnace structure has an important influence on the temperature distribution, which is also the key to improve the thermal efficiency of the system and the quality of radioactive waste treatment. In this paper, the finite element software COMSOL is used to carry out three-dimensional steady-state numerical simulation of the plasma melting furnace, focusing on the impact of the furnace structure on the waste treatment capacity. Through the establishment of mathematical models, combined with fluid dynamics theory and multi-physical field coupling nodes to calculate the interaction between the physical fields, the temperature field and velocity field inside the furnace body are calculated, and the calculated results are compared with the experimental data, and the relative error is 11.62%. And compare and analyze the influence of different structures on the temperature field and material handling effect, to provide theoretical guidance for the optimization of furnace structure design and thermal efficiency improvement.