Absorber Feed Tank (AFT) structure is a composite structure of concrete structure supporting slurry tank in power plant desulfurization process. The field monitoring of AFT structure in a thermal power plant in Chifeng City shows that the slurry in the slurry tank shakes greatly during the operation of slurry mixer, and the slurry constantly impacts the tank wall, which aggravates the structural vibration and seriously affects the structural safety. In order to solve this problem, an movable anti-sloshing plate device was proposed in the slurry tank to reduce the slurry sloshing wave height in the slurry tank during the operation of the equipment, so as to reduce the vibration of AFT structure. The fluid structure coupling model of AFT structure slurry anti-sway plate was established by using ADINA finite element software. The dynamic time history analysis of the structure under normal operation and near-field and far-field earthquake was carried out. Four data monitoring points were selected to monitor the sloshing wave height of slurry liquid level and tank top displacement. The results show that the slurry sloshing wave height gradually decreases from the edge to the center of the slurry tank. After adding the anti-sloshing plate device, the slurry sloshing wave height and the vibration displacement of the slurry tank top decrease under normal operation state and near-field and far-field action. The movable anti-sway plate device has a certain control effect on the vibration of AFT structure.