Based on the principle of Moiré Deflection Technology (MDT) and the definition of lenses’ power,relationship between moiré fringes’ tilting angle and the tested lens’s power is deduced respectively according to the combination of Talbot effect and principle of grating shadow and Fresnel-Kirchhoff theory. The calculated results are uniform that is lenses’ power is in the direct ratio to the tangent of moiré fringes’ tilting angle. Some factors that will affect the measuring error of lenses’ power are discussed. Analysis of the results shows that measurement of lenses’ power using MDT has high precision and it is feasible for lenses with low or middle-high power if proper period of gratings and reasonable angle between the two gratings are adopted. In the end,images of moiré fringes gotten by a single lens,an aspheric lens and a progressive addition lens are provided and analyzed.