Abstract: Using the twodimensional symmetric incompressible laminar N-S equation, a numerical simulation of the fully developed laminar flow of axially symmetric periodic divergingconverging tubes at Reynolds number 100 to 1300 and of the relevant heat transfer characteristics, is carried out with finite volume method and SIMPLE algorithm, with emphases putting on the relationships between different Reynolds numbers, geometries and heat transfer intensities. The computational results are analyzed by field synergy analysis theory. Variations of convection heat transfer intensity versus Reynolds number and geometry are obtained under the laminar flow. The simulation is of practical importance for studying heat transfer enhancement characteristics and developing heat transfer techniques.