The quantitative relation of hologram information capacity with parallax and field angle is computed. The result points out that there is a mass of information in order to provide adequate parallax and field angle for three-dimensional display. With enough parallax and field angle, the limit of information reduction is given, and the characteristics of reconstruction image of grating sampled hologram (GSH) is analyzed. A design for using the GSH to three-dimensional displaying is proposed. This work can be guidance for fast computing hologram and holographic video.