Numerous hydrological modeling studies have been carried out in several basins with various climatic, land-use, soil, and geological conditions. The applied models have different structure to simulate discharge. conducting comparative analyses of models and identifying better models which represent realistic simulation is important for proper development and management of water resource for the watershed. The main objective of this study is to conduct comparative analysis of rainfall-runoff modeling using HEC-HMS and PED-W Models and its relative strength to simulate discharge for Mersa River watershed. A successive seventeen years (1996-2012) hydrometeorological data were used for comparisons of these models. For this study's comparison of these hydrological models, hydro-meteorological data analysis, sensitivity analysis, calibration, and validation were completed. From the parameters of PED-W model hill side area and maximum water storage were very highly sensitive parameter for runoff estimation in the selected watershed. These parameters were very flexible when changing its value. The HEC-HMS model's most sensitive parameters were surface maximum storage, SMA maximum infiltration and SMA soil storage. These sensitive parameters were grouped under the loss model. The model efficiency measurement techniques were Nash Sutcliff efficiency (NSE), coefficient of determination (R 2 ) and root mean square error (RMSE). The corresponding value of the PED-W and HEC-HMS models during daily calibration period were, (0.666, 0.664), (0.705, 0.695) and (1.31, 0.6) of NSE, R 2 and RMSE value respectively. Similarly for validation period were (0.55, 0.542), (0.674, 0.555) and (1.61, 0.7) of NSE, R 2 and RMSE value respectively. Based on these objective function outputs PED-W model had better performance.