The utility model provides a big circular sedimentation tank of tripe, from the top down divide into in proper order upper portion regional 1, go up transition region 2, middle part regional 3, transition region 4, lower region 5 down, 3 regional diameters at the middle part are the biggest, and 1 regional diameter on the upper portion is slightly little, and the lower region 5 diameter is minimum, the upper end on upper portion regional 1 is equipped with annular water collecting tank 7, transition region 2 is gone up in upper portion regional 1 and middle part region, is the cone and connects, and go to the bottom and respectively install the horizontal stainless steel meshwork of one deck in the top on last transition region 2, installs the filler between the two -layer net, and mesh aperture is less than the filler external diameter, it is connected to be the radius cone between middle part regional 3 and the lower region 5, there is a central inlet tube 6 from 1 regional central downwardly extending on the upper portion to 3 regional centers at the middle part, bottom from lower region 5 is connected with mud pipe 8, returns mud pipe 9, it links to each other with central inlet tube 6 through circulating pump 10, circulating line 11 to return mud pipe 9. It is little that the water yield is handled in the effective solution of this invention, and suspended solid concentration is high, and the poor problem of solid -liquid separation effect improves and separates the effect, and it is high that the underflow contains concentration admittedly.