The Laoha River catchment, Liaohe River Basin in the semi-arid region of northern China is selected for study.The interception evaporation, canopy transpiration and soil evaporation are computed by a physically-based two-source potential evapo-transpiration model in each grid cell of the basin.The calculated potential evapotranspiration is regarded as the input of the hybrid runoff model instead of the pan evaporation.Then the grid-based distributed hydrologic model is built for daily runoff simulation during 1970-1979 in the target basin by coupling the two-source PET model in the hybrid runoff model framework.The results show that the two-source PET model can reflect the effects of vegetation type, vegetation physiological features and phonological characteristics on the evapotranspiration.And the grid-based distributed hydrologic model which can illuminate the rule of runoff generation and runoff routing is applicable for runoff simulation in the target basin.