Abstract: In the Jiangsu reach of the Yangtze River, one of the most common silting-promoting structures in the cave collapses is tree top-stone. As cutting trees has negative impact on greening and ecology, a kind of curtain-stone composed of floating block, cloth (or geotextile) and stone is invented. This curtain-stone can block the flow and promote the siltation, which is seldom studied. Based on the force analysis of the curtain-stone placed in the equilibrium state in the flow, the differential equations of the forces acting on the curtain-stone micro element are listed, and then the distribution curve (surface) of the curtain-stone along the water depth can be solved, and the relevant coefficients in the curve are determined from the test data. The formula can be used to determine the horizontal projection length and buoyancy of curtain-stone, and also explain the mechanical mechanism of the floating block floating on or submerged in the water, and the curtain floating on or submerged in the river bottom. A local model of the pit collapse near Zhinan village in the Yangzhong section of the Yangtze River is established. The water blocking effects of curtain-stone and tree head-stone are compared in the scour pools of the model. And the water blocking effect results are the same. The use of curtain-stone can reduce the impact on ecology.