MicroRNA-155　(miR-155)　can　act　as　a　suitable　biomarker　for　dry　eye　diseases　caused　by　Sjogren＇s　syndrome.　Since　the　concentration　of　miR-155　in　the　clinic　samples　is　low,　it　is　necessary　to　develop　some　simple　but　sen-sitive　detection　methods.　In　this　study,　a　homogeneous　electrochemiluminescence　(ECL)　biosensor　for　miR-155　detection　based　on　catalyze　hairpin　assembly　(CHA)　and　hybridization　chain　reaction　(HCR)　and　magnetic　assisted　enrichment　had　been　constructed.　Firstly,　biotin-modified　hairpin　H1　(bio-H1)　had　been　connected　with　the　streptavidin-modified　magnetic　beads　(SAMBs)　to　capture　target,　which　can　be　used　to　trigger　CHA　reaction　to　complete　the　first　signal　amplification　with　the　assistance　of　hairpin　H2.　Then　the　stick　end　of　H2　of　the　CHA　production　can　trigger　the　HCR　reaction　of　H3　and　H4　and　generate　long　double-stranded　DNAs　(dsDNAs)　on　the　surface　of　SAMBs　to　realize　the　second　signal　amplification.　Ru(phen)32+　can　insert　into　the　dsDNAs　to　produce　SAMBs/dsDNA/Ru　and　act　as　signal　tags,　which　can　be　purified　by　magnetic　separation　easily,　making　the　background　signal　significantly　reduced.　The　ECL　intensity　of　the　system　had　a　linear　rela-tionship　with　logarithm　of　miR-155　concentration　in　the　range　of　1　fM　similar　to　10　nM,　with　a　detection　limit　as　low　as　0.63　fM.　The　proposed　biosensor　had　been　applied　to　monitor　miR-155　in　clinical　samples　with　satisfied　results.