This study has been concentrated on carrying out the numerical analysis of the residual stresses in the centrifugally cast duplex tube reheated from 20℃ to 1050℃ after it had been already made by the centrifual casting process. The finite difference method was used to analyze the unsteady state time dependent thermal problem, while the computation of the residual stresses enforced to adopt the finite element method based on finite deformation elasticity theory. The temperature difference at each node produced from the thermal analysis at each time step was taken as an imput data to calculate the thermal stresses. In order to solve the nonlinear system equations, the Newton-Raphson iterative method was used, and the results were compared to those of running the commercial package, ANSYS50 for verification. STS 410 and STS 304 were chosen for materials of the model of the duplex tube in this research. The results made from the numerical analysis draw the conclusions as follows. First, the rapid decrease of the duplex tube, and it was considered that it would bring out the crack of the tube. In a while, in the case of the furnace cooling, the hoop stresses in the outer and inner surface increased linearly with stable status. Secondly, the cooling method had an effect just on the change of the thermal stresses through time, but the residual stresses finally remained in the tube were the same for each cooling case regardless of the cooling method.