In this paper a new interface capturing scheme, THINC (tangent of hyperbola for interface capturing) scheme, is incorporated into our CFD code for the numerical simulation of violent sloshing in a 3D rectangular tank. The THINC scheme is superior as an interface capturing scheme in that the numerical diffusion is less and the mass conservation is good even for long-term computations of violent sloshing. These excellent features of the THINC scheme are demonstrated with some preliminary numerical examples.