A stability analysis has been made for a newly designed gate of intake tower of reservoir. The analysis is composed of finding the natural frequency of the gate and the frequency induced by water flowing over and through the gate. ANSYS is employed to calculate the natural frequency of the gate and SC/Tetra is utilized for calculating flow field around the gate, which in turn gives the frequency of pressure force fluctuation on the gate. In addition to the safety analysis, the present study presents how the gate selectively intakes a muddy water layer located in the middle depth of reservoir.