Most　of　single-component　white-light-emitting　materials　focus　on　organic-inorganic　hybrid　perovskites,　metal-organic　frameworks,　as　well　as　all-inorganic　semiconductors.　In　this　work,　we　successfully　assembled　an　all-inorganic　layered　perovskite　by　mixing　two　halogens　of　distinct　ionic　radii,　namely,　Rb2CdCl2I2,　which　emits　warm　white　light　with　a　high　color　rendering　index　of　88.　To　date,　Rb2CdCl2I2　is　the　first　single-component　white-light-emitting　material　with　an　all-inorganic　layered　perovskite　structure.　Furthermore,　Rb2CdCl2I2　is　thermally　highly　stable　up　to　575K.　A　series　of　luminescence　measurements　show　that　the　white-light　emission　arises　from　the　lattice　deformation,　which　are　closely　related　to　the　[CdCl4I2](2-)　octahedra　with　high　distortion　from　the　distinct　ionic　radii　of　Cl　and　I.　The　first-principles　calculations　reveal　that　both　the　Cl　and　I　components　make　significant　contributions　to　the　electronic　band　structures　of　Rb2CdCl2I2.　These　findings　indicate　that　mixing　halogens　is　an　effective　route　to　design　and　synthesize　new　single-component　white-light-emitting　materials.