Abstract: Based on the structure and operational characteristic of a new type of steam generator,a graphical model is designed using simulation software.Operating parameters of the casing once-through steam generator is simulated under different load condition.The thermal hydraulics characteristic is analysed and compared to the specific program.The simulating results fit theoretical analysis,showing that the steam generator can be simulated correctly and precisely.Reference and guidance can be provided for the design of dual layer heat transfer once-through steam generator and related systems.