On thermoplastic-photoconductor media, the holographic characteristics and the enhancement of sensitivity for light intensity have been studied and it is found that the diffraction efficiency depends strongly upon the intensity of laser light and that the sensitivity becomes higher as the thickness of single layer photoconductor increases. Double layer and a triple layer photoconductor systems which are more sensitive than a usual single layer have been developed. The most sensitive photoconductor system is a triple layer photoconductor system, that is PVK+CV*10:4 PVK:TNF complex+BG*10:4 PVK:TNF complex, the critical intensity is less than 1 erg/cm².s and is about a tenth of that of a usual single layer. The main reason for the sensitivity enhancement of the triple layer photoconductor system is to absorb the charge carriers which are injected or cannot arrive at the transparent conductor. Another reason is to make a kind of inclination in the distribution of charge carriers created by an exposure to a laser light in order to make strong the Coulomb's force.