  This paper is concerned with a diffuse interface model called as
Navier-Stokes/Cahn-Hilliard system. This model is usually used to describe the
motion of immiscible two-phase flow with diffusion interface. For the periodic
boundary value problem of this system in torus $\mathbb{T}^3$, we prove that
there exists a global unique strong solution near the phase separation state,
which means no vacuum, shock wave, mass concentration, interface collision and
rupture will be developed in finite time. Furthermore, we established the large
time behavior of these global strong solution of this system. In particular, we
find that the phase field decays algebraically to the phase separation state.
