Flood is a natural phenomenon, which human being has experienced from very old times. In Iran, due to its very large area, several climates, and time and local density of Precipitations in most watersheds, there are many great floods of the country. In this study, run-off coefficient, maximum debit of flood, identifying the factors and elements that are effective on floodiness, and zoning of the area of Leilan chai watershed based on its flood bearing are analyzed. The curve number method was used for this watershed. To do this, firstly, the needed data and information including the statistical situation of the area climates and satellite images were gathered Inputted to the GIS data system. Compiling these data and information by the SCS method and the CN of the watershed, The infiltration level and run-off volume were prepared. Finally, the zoning map of the annual flooding potential of the area were produced using weighting model and compiling the area Precipitation, hydrological groups of soil, slope level, land use, etc.