The setup of the moir$acute{e}$ deflectometry using the virtual grating was done, so the convergence and divergence of a pencil of ray was determined. The light source was He-Ne laser(3mW). The focal length of the first lens, the second lens being 18 mm, 250 mm respectively was used for the setup of the beam expander. The optics of the moir$acute{e}$ deflectometry determining the vergence was used a diffraction grating(pitch = $1.6{mu}m/line$) and a front flat reflection mirror. The effective focal length of the trial lens set was measured and compared with the theoretical value.