Base on the principle of digital holographic interferometry, two lensless Fourier transform holograms representing two different deformation states of object field are captured by CCD. Then the numerical reconstruction of digital holograms is implemented respectively to acquire the complex amplitude of object waves, and the interference phase difference is determined by subtracting the phases of the different states. According to the pure bending theory in elastic mechanics, the Poisson′s ratio is derived numerically from the angle between the asymptotic lines of the fringes of equal phase, which are caused from homogeneous deformation and reconstructed by digital holographic interferometry. This method for determination of Poisson′s ratio of material in the full-access performance by experiment is simple and easy to operate, especially suitable for material with rough surface, low value Poisson′s ratio and small size.