We studied parallactic theories and techniques about the system of digital synthetic generated hologram.We used two different SLM:thin film transistor liquid crystal display(TFT-LCD) or digital micromirror device(DMD).The comparison between the two SLM is listed.Then the experiment was done using TFT-LCD as modulator of digital synthetic holography system.and we get a piece of digital synthetic hologram.The result proved that the digital-synthetic holoraphy system is realizable and useful.