Steam generator is optimized by applying entransy dissipation extremum principle and constructal theory and adopting analyti-cal method.The obtained results show that the optimal spacing between adjacent tubes,the mass flow rate of gas and the maximum entransy dissipation rate all depend on the dimensionless diameter of one tube,the dimensionless pressure difference number and the dimensionless length of flow channel of gas.Besides the three dimensionless groups,the optimal numbers of riser tubes and downcomer tubes and their summation all depend on the dimensionless height of one tube.The maximum entransy dissipation rate increases as the pressure difference that drives the gas flowing increases,and as the diameter of one tube and the length of flow channel both decrease.The mean heat flux in the heat transfer process of hot gas grows greatly,and the performance of the system is improved.Compared with the optimal construct with heat transfer rate maximization,the optimal construct with entransy dissipation rate maximization can improved the heat transfer effect of the steam generator more. Steam generator is optimized by applying entransy dissipation extremum principle and constructal theory and adopting analyti-cal method. The obtained results that that the optimal spacing between adjacent tubes, the mass flow rate of gas and the maximum entransy dissipation rate all depend on the dimensionless diameter of one tube, the dimensionless length of flow channel of gas. Besides the three dimensionless groups, the optimal numbers of riser tubes and downcomer tubes and their summation all depend on the dimensionless height of one tube. maximum entransy dissipation rate increases as the pressure difference that drives the gas flowing increases, and as the diameter of one tube and the length of flow channel both decrease. the mean heat flux in the heat transfer process of hot gas grows greatly, and the performance of the system is improved. Compared with the optimal construct with heat transfer rate maximization, the optimal construct wit h entransy dissipation rate maximization can improved the heat transfer effect of the steam generator more.