The　realization　of　multi-level　storage　of　chalcogenide　phase　change　materials　(C-PCMs)　has　been　proved　to　be　an　effective　way　to　achieve　high-density　data　storage.　However,　Ge2Sb2Te5　(GST),　as　one　of　the　most　representative　C-PCMs,　has　poor　performance　in　multi-level　storage.　In　this　paper,　a　bi-layer　composite　structure　GST-nAg　was　proposed　and　prepared　by　magnetron　sputtering　accompanied　by　thermal　annealing.　Microstructure　and　multi-level　optical　properties　of　GST-nAg　were　investigated　using　x-ray　diffraction,　scanning　electron　microscopy,　variable　angle　spectroscopic　ellipsometry,　Raman　spectrometer,　micro-area　reflectivity　testing　system,　etc.　The　results　showed　that　the　formation　of　the　Ag　nanoparticles　layer　changed　the　heat　distribution　and　heat　transmission　in　the　GST　layer　when　irradiated　by　a　nanosecond　pulsed　laser.　By　changing　the　laser　fluence,　the　microstructure　of　the　GST　layer　could　be　adjusted　and　ten　crystal　states　with　different　optical　reflectivity　were　obtained.　In　addition,　the　introduction　of　Ag　nanoparticles　reduced　the　compressive　stress　among　the　Ge/Sb-Te　tetrahedral　structure　and　grain　size,　which　benefits　to　the　formation　and　stable　existence　of　more　crystal　states.　Finally,　an　optical　irradiation　device　based　on　GST-nAg　was　built　and　the　storage　density　of　this　optical　irradiation　device　was　increased　about　three　times.　This　paper　provides　a　way　to　realize　multi-level　optical　storage.