Taking two-dimensional （2D） exhaust system of turbofan engine as an example， the multi-objective contour optimization design of thrust and infrared characteristics of exhaust system was studied when the engine is in military power on the ground. The optimization objectives were thrust coefficient and infrared radiation （IR） characteristics at 3—5 μm in the positive tail direction of exhaust system. The constraint conditions were the IR characteristics of the narrow side detection plane at 30° and the wide side detection plane at 90°. The optimization variables were throat aspect ratio， throat radius ratio， convergence half angle and divergent half angle. In the design process， the initial sample points were determined by orthogonal experimental method. The RBF surrogate models of thrust coefficient and IR characteristics of exhaust system were established. The analysis and optimization was conducted with the adaptive simulated annealing algorithm. The results show that the multi-objective optimization method can be applied to the compatible design of thrust and infrared characteristics of exhaust system with good effects. The thrust coefficient of multi-objective optimized exhaust system is increased by 5.3% compared with the baseline 2D model. The dimensionless integral radiation intensity in the positive tail direction is reduced by 17%.