2,　2＇-azinobis-3-ethylbenzthiazoline-6-sulfonate　(ABTS),　3,　3＇,　5,　5＇-tetramethylbenzidine　(TMB),　o-phenylenediamine　(OPD)　are　typical　chromogenic　substrates　to　evaluate　the　activity　of　peroxidase-like　nanozymes.　However,　these　substrates　are　toxic,　unstable,　and　the　coloration　reactions　are　slow.　Herein,　the　classical　starch-sodium　iodide　reagent　was　utilized　as　the　chromogenic　substrate　to　evaluate　peroxidase-like　activity　of　nanozymes.　Starch-sodium　iodine　is　less　toxic,　more　stable　and　faster　color　reaction　than　ABTS,　TMB　and　OPD.　Under　the　catalysis　of　peroxidase-like　nanozymes　such　as　Mo5N6　nanosheets,　graphene　oxide　nanosheets,　Fe3O4　nanoparticles,　CeO2　nanoparticles,　iodide　ion　(I-)　is　oxidized　by　H2O2　to　produce　blue　color　complex　(starch-I-2).　Taking　Mo5N6　nanosheets　as　the　peroxidase-like　nanozyme,　the　color　reaction　completed　within　5　min　at　room　temperature　(25　degrees　C),　and　the　chromogenic　substrate　remained　stable　within　30　days.　The　maximum　reaction　rate　(V-max)　using　starch-sodium　iodine　as　the　chromogenic　substrate　was　more　than　100-fold　higher　than　that　of　TMB.　Based　on　this,　a　sensitive　colorimetric　sensor　and　facile　portable　agarose　gel　test　kits　were　proposed　and　applied　for　the　detection　of　H2O2　residue　in　liquid　milk　samples　with　fast　response.