Development　of　simple　but　sensitive　biosensor　for　influenza　detection　is　highly　important　in　immediate　and　effective　clinical　treatment.　In　this　study,　a　sensitive　colorimetric　immunosensor　which　combines　the　advantages　of　high　selectivity　of　immunoassay　and　simplicity　of　colorimetric　detection　has　been　developed　to　detect　influenza　virus　H5N1　based　on　enzyme-encapsulated　liposome.　Biotin-tagged　liposome　encapsulated　with　large　amount　of　horseradish　peroxidase　(HRP)　was　firstly　synthesized.　In　the　presence　of　H5N1,　H5N1　co-bound　with　the　capture　antibody　and　the　biotinylated　detection　antibody　to　form　sandwich　immunocomplex.　Subsequently,　the　HRP-encapsulated　liposome　was　introduced　to　conjugate　with　the　detection　antibody　through　biotin-avidin-biotin　linkage.　Upon　the　addition　of　substrate　(mixture　of　3,3′,5,5′-tetramethylbenzidine　(TMB)　and　H　2　O　2　),　the　liposome　was　directly　lysed　to　release　large　amount　of　HRP　by　TMB.　The　released　HRP　catalyzed　the　H　2　O　2　-mediated　oxidation　of　TMB,　resulting　in　color　change　of　the　system,　which　was　observed　by　naked　eyes　or　UV–vis　spectra.　The　result　showed　that　the　absorption　intensity　enhanced　with　the　increase　of　H5N1　concentration　ranging　from　0.1　to　4.0 ng/mL,　and　the　detection　limit　was　calculated　to　be　0.04 ng/mL.　The　sensitivity　of　the　proposed　biosensor　is　much　higher　than　that　of　conventional　enzyme-linked　immunosorbent　assay　method.　The　proposed　immunosensor　is　relatively　simple,　low-cost,　sensitive,　and　selective　without　using　any　sophisticated　instruments,　therefore　it　may　have　a　promising　prospect　for　detecting　targets　in　clinical　medicine,　food　safety　analysis,　and　environmental　monitoring.　©　2017　Elsevier　B.V.