Abstract: To achieve the overall numerical simulation of heat exchanger performance, a new method named “simulation in subsections, integration of the whole” for numerical simulation of shell & tube heat exchanger was proposed. The core idea was, based on the qualitative analysis of the flow passage and the performance of hydrodynamics and heat transfer of heat exchanger, dividing the inner flow passage into subsections, and then the whole 3D geometrical and meshed submodels of typical subsection flow passage were set up. By establishing the continuity conditions between submodels, the meshed submodel was simulated continuously，and the solved local data weres combined into the whole result.