Dielectric property of two-phase stack-up sample is studied by electric force microscopy (EFM). Highly oriented pyrolytic graphite (HOPG)/polyethylene(PE) and mica/PE are fabricated. The phenomenon that phase shift (Δθ) of conducting probe varys with dielectric constant of material is discovered near the interface between the two materials by using phase detection EFM. The characteristic curves of tan(Δθ) versus tip voltage VEFM are of parabolic type. Quadratic coefficient increases with dielectric constant ε increasing. An approach to the qualitative analysis of the dielectric property near the interface between different material at the micro/nanometer scale, is provided in this paper.