Abstarct: Outlet gates have attracted a great attention in dam engineering and related industry. In this regard, the tasks of many investigations are focused on providing the discussion and solutions of related problems for such structures. Increasing the velocity and pressure reduction are the common problems in high head conduits, which lead to cavitation formation. Cavitation is the main factor of sever damages in outflow tunnels downstream of gates; therefore, it is necessary to decrease or eliminate its destructive impacts on the structures. The main aim of this research is to study the effects of gate lip on flow domain downstream of outlet gates in no-aeration condition. Experimental studies are utilized to calibrate the numerical model of flow around outlet gates. The physical model was the Dam of Zhaveh-Iran, constructed and tested at Water Research Institute of Iran. Then, a numerical model was provided and calibrated by experimental results. To take into account the effect of gate lip on cavitation of outlet gates, gate lip angles of 22.5 and 45 degrees with gate openings of %50 and %70 were simulated, numerically. Two heads of 2m and 5m were also used to determine the velocity and pressure field. The results showed the reasonable agreements between the numerical and experimental information. It is also concluded that, increasing the gate lip angle has significant effects and changes the flow characteristics and thus, cavition index of flow around the outlet gates.