Abstarct: The development of residential and urban areas on the banks of rivers and flood plains increases the risk of flooding regardless of the hydrological and hydraulic conditions governing the river. Flood simulation with hydrological models requires proper input precipitation data, which unfortunately, in most of the country's basins, there is no proper distribution of rain gauge stations and long-term data. For this purpose, the use of satellite precipitation data with high spatial and temporal resolution to solve this gap can be beneficial. Therefore, the purpose of this research is to investigate and use satellite precipitation products as input to hydrological models for simulating floods in a part of the Mahabadchai basin. In this regard, first the performance of these products was evaluated in the position corresponding to the ground station and on a daily scale. For this purpose, various statistical parameters such as coefficient of determination (R2), root mean square error (RMSE) and Kling-Gupta evaluation criterion (KGE) as well as conformity indices such as probability of detection index (POD), false alarm ratio (FAR), success index Then using the multi-criteria decision-making method, IMERG was identified as the selected product by determining the concentration time of 2, 5, 15 and 25 years. The conceptual model of the catchment was defined in the HEC-GeoHMS software environment and introduced as an input to the HEC-HMS software for rainfall-runoff modeling The laxyers of the waterway, left and right banks, cross-sections, etc. were used for the input to HEC-RAS. After correcting the cross-sections, Manning's coefficients were defined baxsed on the land use map for the model. Then, by selecting the mixed flow regime The flood zones corresponding to different rainfalls were simulated. The results showed that the flood zone resulting from the IMERG rainfall product with a return period of 2 and 5 years is about 5 to 10% larger than the flood zone resulting from the observed rainfall. On the other hand, the flood zone resulting from the IMERG precipitation product with a return period of 10, 15 and 25 years is about 6 to 10% smaller than the flood zone resulting from observed rainfall.