With the help of mathematical models, complex hydraulic conditions and especially the presence of two-phase flows over spillway chutes can be simulated in three dimensions with acceptable accuracy. By establishing different flow flows, the possibility of vacuum generation in this structure can be examined. In the present study, the possibility of cavitation and cure on the service spillway of Aghchai dam using numerical methods in Flow-3D software is evaluated. The flood flow regime has 4400 and 1065 cubic meters per second rate, which is provided by the project consultant. The free flow level in this model is calculated by volume of fluid (VOF) method. The results of flow simulation at a flow rate of 4400 cubic meters per second show that cavitation is very likely to occur at the ogee and the angle change of the chute channel where should be prevented by taking some actions. However, in lower flows, such as 1065 cubic meters per second, due to lower speed and lack of separation of flow from the bed, the occurrence probability of vacuum generation is low and not very significant. The results obtained are in good agreement with the results of the project consultant.