In order to dispose oily sludge, a vertical multi-layer rotating disc pyrolysis furnace is developed independently. The high-temperature gas generated in the combustion chamber provides heat for the pyrolysis furnace. Therefore, the thermal efficiency and safety of the combustion chamber are the guarantee for the stable operation of the entire pyrolysis furnace. In order to determine whether the new pyrolysis furnace structure was safe and feasible, the temperature field and deformation field of the combustion chamber under different structural parameters were studied by using the fluid-thermal-solid coupling method of ANSYS Workbench, and the structure of the combustion chamber of the pyrolysis furnace was optimized by exploring the parameters of the baffle. The results showed that the structural performance of the baffle in the combustion chamber was better than that without baffle. The variation range of the temperature field variation coefficient of the combustion chamber with the baffle was 0.06 smaller than that without baffle, and the temperature field distribution was more uniform. The maximum deformation of the combustion chamber appeared on the partition between the combustion chamber and the pyrolysis chamber. The maximum deformation of the combustion chamber with baffle was 80% less than the maximum deformation of the combustion chamber without baffle, and the maximum deformation with the increase of the position of the baffle to the centre or the length of the baffle showed a trend of first decreasing and then increasing, and the thickness of the baffle had the least influence on the deformation field. When the baffle position was 150 mm, the length of the baffle was 800 mm, and the thickness of the baffle was at 14 mm, the structure of the combustion chamber of the new pyrolysis furnace was optimal. The use of fluid-thermal-solid coupling method for the optimization design of such combustion chamber structure had more reliable engineering significance, and it also provided technical support for the subsequent industrial application of oily sludge pyrolysis technology.