Bistable-state　dielectric　properties　without　maintaining　external　stimuli　after　switching　are　highly　desirable　for　nonvolatile　memory　devices;　however,　research　on　switchable　dielectric　materials　was　mostly　limited　to　the　stimulation-constant　mode.　This　work　reports　a　record-high　dielectric　permittivity　gain　through　the　bistable-state　modulation　mode　in　two　photochromic　semiconductors　(PSCs),　and　reveals　the　general　structure　characteristic　and　intrinsic　physical　reasons　for　the　increase　of　dielectric　permittivity.　This　discovery　will　guide　the　design　for　switchable　dielectric　materials　with　dielectric　permittivity　gain　in　the　future.　©　2021　American　Chemical　Society.