Abstarct: Protection of downstream facilities of dams against floods discharge, reducing flow energy and directing it to downstream, are among the most important issues in the process of studies and design. Several solutionshave been suggested to solve this problem, including stilling basin. However, a more suitable solution is to disperse the flow energy while it is passing on the spillway. For this reason, stepped spillways have received attention as an effective and suitable solution. These spillways show highly complicated behaviors; however to this date, most researches have merely studied the effects of various factors on the process of variation of energy dissipation; thus, it seems necessary to study other factors (especially pressure field) along this subject. Due to the high expenses and problems in making lab studies on one hand, and successful experiences in computational fluid dynamics encouraged researchers to use numerical methods in conducting the researches. In the present research, FLOW 3D software was used as a modeling tools after measuring its accuracy and gaining confidence of its proper function in simulating flows on those spillways; and, by changing a series of effective hydraulic parameters such as spillway slope, proportion of cascade dimensions, The flow behavior in those spillways were studied. It was observed that exercising those changes in line with achieving the highest rate of energy dissipation could not be considered as the most essential criteria in designing as it and might give way to the emergence of problems in proper performance of the overflow as well as creating risks (such as sharpe fall in pressure, possibility of cavitation danger in some parts); therefore, in the initial studies, the effect of changes made on all effective factors must be studied simultaneously.