In order to know thoroughly the thermal deformation characteristics of the dry gas seal in the synthesis gas compressor, the physical model and the thermal equilibrium model of the seal pair are established on its structural and thermal analysis. Based on finite element analysis software ANSYS, separation method are applied to resolve and analyze the temperature field and thermal-structural coupling deformation of the seal pair. The analyzed results show that the temperature of the rotating ring decreases gradually from the end face to the back face, and decreases gradually from the inner radius to the outer radius. The maximum of the temperature gradient of the rotating ring locates at the outer radius of the end face.The deformation of the stationary ring is negative conicity, the deformation of the rotating ring is positive conicity, and the later is the major reason of seal failure. Because of the thermal deformation, the end faces will form a convergent wedge. The convergent wedge favors the formation of a gaseous film, but it will lead to a increase in leakage quantity.