The mixes of normal concrete is a kind of coarse dispersible system. The cohesion between its grains is small. When the normal concrete is placed directly in water, the mixes will be dispersed easily by the action of water, leading to the loss of cement, segregation and layering of sand and stone, which changes the concrete grading composition, makes its strength decrease and pollutes water quality. The nondispersible underwater concrete (NDC) is made by adding flocculating agent or polymerizer, which emphatically improves the composition, mixing proportion and properties of concrete. NDC increases the cohesion and anti water dispersity of concrete itself, and radically solves the quality problem of underwater concrete.