With fluid-structure interaction effect considered, the key factor in the analysis of flow-induced vibration of the sector gate is to get self-vibration characteristics. Adopting the finite element numerical method, we get the self-vibration frequency and the modal characters of the sector gate in different water level conditions. The gates are made to decrease its self-vibration frequencies and change modal characters, which are shown by calculations. Reasonable suggestions on the safe operation of the gate are put forward on the basis of computation and analysis.