The mechanism of the fluid-solid coupled vi-bration is analyzed as the fluctuating pressure acts on the inletand the outlet slits of a slab. The parameter multinomialmethod was exploited to calculate the pressure field within thejoints of the slabs by solving the basic equations of the oscilla-tion flow. The calculated result shows that the time-averageduplift increases with the increase of the length of the slab andis large in the middle and is small in both sides. The time-av-eraged uplift reduces with the increase of water depth, and thefluctuating uplift reduces rapidly with the increase of thethickness of the slit. The calculated result is in agreementwith the experimental results.