Recent　optical　stimulation　suggests　a　vital　non-contact　pathway　to　manipulate　both　macroscopic　and　microscopic　ferroelectric　properties　and　paves　the　foundation　for　optoelectronics　devices.　However,　up　to　date,　most　optical-related　manipulation　of　ferroelectric　properties　is　restricted　due　to　their　intrinsic　bandgap　and　limited　visible　light　spectrum　absorption.　Here,　we　reveal　non-oxide　Sn2P2S6　single　crystal　possesses　full-visible-spectrum　absorption　(from　300　to　800　nm)　with　a　unique　disproportionation　mechanism　of　photoexcited　Sn　ions　and　Urbach　tail,　which　is　not　contradicting　to　the　intrinsic　band　gap.　Interestingly,　we　observed　the　existence　of　conductive　domain　walls　(c-DW)　and　the　light　illumination　induced　significant　enhancement　of　the　domain　wall　conductivity　caused　by　such　disproportionation　reaction.　In　addition,　the　domains　separated　by　c-DW　also　exhibited　noticeable　electrical　conductivity　difference　in　the　presence　of　optical　illumination　owing　to　the　interfacial　polarization　charge　with　opposite　signs.　The　result　provides　a　novel　opportunity　for　understanding　the　electrical　conductivity　behavior　of　the　domains　and　domain　walls　in　ferroelectrics　with　full-visible-spectrum　absorption　and　achieving　greatly　enhanced　performances　for　optoelectronics.