The holographically-formed polymer dispersed liquid crystal (H-PDLC) has been widely studied in recent years. In this paper, we analyze the major factors contributing to the efficiency of volume gratings base on the basic optical theory. With regard to the feature of the special exposure material-PDLC, we have conducted some experiments to investigate the impacts of four major factors, such as different recipes of PDLC, exposing time of PDLC cells, thickness of film and the degree of two laser beams, which contribute to obtain the higher diffraction efficiency. As a result, under the same conditions, it is found that the most significant affecting factor is the recipe of PDLC. The diffraction efficiency is enhanced substantially after new chemistry reagent is mixed into the polymer precursors. Shorter cure time and comparative smaller degree of two laser beams give rise to higher diffraction efficiency. Finally, using 17degree of two laser beams, 50mw power of laser with the wavelength of 441.6 nm and exposing time about 30 seconds, we can obtain about 90% efficiency of the H-PDLC volume grating. Furthermore, we researched the relationship between the applied voltage and the diffraction efficiency.