Abstract: In this paper, the capacitance probe and high speed camera were adopted to study the wave structure of the falling film on the flat plate experimentally. Two typical shape waves were studied numerically based on the experimental data. The wave shape kept invariant and the shear stress by the air was neglected in the numerical calculation. The numerical calculation was carried out to investigate the flow behaviour and heat transfer characteristic inside the surface wave. The results show that the vortices inside the surface wave have great effect on the heat transfer for sub-cooled falling film. The enhancement of the heat transfer induced by the large amplitude wave consists of two parts: Convection effect and vortices inside the surface wave which reduce the equivalent film thickness by carrying large mass and momentum