Lead-based　halide　perovskite　nanomaterials　with　excellent　optical　properties　have　aroused　great　attention　in　the　fields　of　solar　cells,　light-emitting　diodes,　lasing,　X-ray　imaging,　etc.　However,　the　toxicity　of　lead　prompts　researchers　to　develop　alternatives　to　cut　down　the　usage　of　lead.　Herein,　all-inorganic　manganese-based　perovskite　derivatives,　CsMnCl3　nanocrystals　(NCs),　with　uniform　size　and　morphology　have　been　synthesized　successfully　via　a　modified　hot-injection　method.　These　NCs　have　a　direct　bandgap　of　4.08　eV　and　a　broadband　emission　centered　at　660　nm.　Through　introducing　modicum　lead　(1%)　into　the　CsMnCl3　NCs,　the　photoluminescence　intensity　greatly　improves,　and　the　quantum　yield　(PLQY)　increases　from　0.7%　to　21%.　Furthermore,　the　CsMnCl3:1%Pb　NCs　feature　high-efficiency　of　X-ray　absorption　and　radioluminescence,　which　make　these　NCs　promising　candidates　for　X-ray　imaging.