In order to understand the role of water/energy exchanges between land surface and atmosphere in runoff formation,in this paper the BATS was applied to simulate runoff,soil temperature and sensible,latent heat fluxes for mountain and plain areas in Huaihe River during flood season in 1991.By using the general method of runoff convergence,the hydrograph at outlet cross-section was estimated. In order to consider the lumped role of geography(plain or mountain) in the runoff generation,the power value of soil moisture in runoff formula was revised. The results show that the error of estimated 50 days flood volume in these cases study is small,the estimated peak time and peak flow are coincident with the observed one basically. The simulated precision of runoff is closely related to that of soil temperature in upper layer.All of these illustrate that the improvement of runoff simulation in GCM is important for appropriate estimation of latent and sensible heat fluxes of land surface to atmosphere.