Some laws on hydrodynamic flocculation of fine sediments found in the circular channel test was elaborated at the beginning of the paper.

As can be seen from flocculation test of CPAM on coal slurry, intrinsic viscosity number, cation degree and medical dosage of CP AM have obvious effect on flocculating performance.

Test result shows the flocculation ability of modified polyacrylamide is strong and has good selectivity, is a sort of good flocculant of hematite.