The invention discloses an eccentric-type arc movable slant board which can be used for accelerating the deposition process in sewage treatment process, clearing a water body, and improving the sewage treatment effect. According to the invention, thin boards are wound to be arc with different sizes, and are ranked at equal or variable distances so as to form groups; an eccentric shaft is fixed on a rotary shaft; the clearances of adjacent arc boards form a plurality of shallow layer deposition tanks; and treated water bodies and settled deposition objects move mutually and stably in the deposition shallow layers and are separated; the eccentric arc slant boars are rotated to shift radially and tangentially, so that water bodies at the shallow layers are subjected to gradient shearing transformation, and flocculant cores are in mutual contact, collide, adhere and polymerize so as to form dense flocculant bodies so as to be separated from water, and raw water is cleared and purified. The eccentric-type arc movable slant board provided by the invention can rotate around the rotary shaft, forms intense and turbulent shearing flows through rapid and reciprocating rotation left and right, is subjected to the high-speed washing effect, and can be used for eliminating possible deposition and blocking conveniently.