For　Li7La3Zr2O12　(LLZO)　solid　electrolytes,　higher　density　usually　means　higher　ionic　conductivity.　Researchers　tried　many　preparation　methods　to　get　high　density　samples　and　at　same　times　to　realize　industrial　production,　low　cost,　scalable　and　fast　synthesis　techniques.　In　this　paper,　the　mainstream　preparation　methods　of　LLZO　was　given,　as　polymerized　complex　method,　sol-gel　method,　field　assisted　sintering,　combustion　technique,　auto-consolidation　method,　water-based　solvent　method.　Among　these　methods,　the　last　four　methods　can　always　increase　the　density　to　more　than　93%.　Especially　the　field　assisted　sintering　method　can　make　the　relative　density　to　be　high　as　99.8%.　And　all　of　these　methods　can　make　the　ion　conductivity　to　be　higher　than　1.4　x　10-4　S　cm-1.　Also,　most　of　these　methods　introduced　the　Al　element　into　LLZO　to　realize　the　liquid　sintering.　©　Journal　of　Physics:　Conference　Series　2021.