In order to reduce complexity of generation of fractional Fourier hologram,according to signal′s fractional Fourier transform and Fresnel diffraction formula,the equivalence relation between them is derived by solving their point spread functions (PSF). So fractional Fourier transform can be transformed into Fresnel diffraction. The object and the hologram plane are sampled by limit of resolution of human eye and size of micromirror of digital micromirror device (DMD). Tiling algorithm is used to generate fractional Fourier hologram,its computation complexity is decreased to O[N2lb(N2/M2)],and a feasible dynamic holographic display is proposed. Finally,the algorithm is verified by DMD holographic display system.