A speed-up reconstruction algorithm of digital holography is studied based on graphic processing unit(GPU) hardware, which can effectively shorten the reconstruction time of digital hologram with powerful parallel computation capacity of GPU. The reconstruction time of two different size digital holograms are compared under GPU acceleration calculation mode and single CPU calculation mode. The result shows that the reconstruction time is shorten to be about 1/15 for a hologram size of 2048 pixel× 2048 pixel with GPU mode. The speed-up reconstruction algorithm of digital holography is designed to be exercisable and universal software, which can satisfy the real-time demand of digital holography system such as display and microscopy and also can instruct rapid setup of digital holography experimental system.