Boron-　and　phenyl-doped　graphitic　carbon　nitride　nanosheets　(BPCN　NSs)　were　prepared　by　thermal　polymerization　of　cyanamide　with　3-aminobenzeneboronic　acid　followed　by　ultrasonic　exfoliation.　BPCN　NSs　exhibited　enhanced　peroxidase-like　activity　and　catalyzed　the　oxidation　of　3,3＇,5,5＇-tetramethylbenzidine　(TMB),　2,2＇-azino-bis(3-ethylbenzothiazoline-6-sulfonic　acid)　and　o-phenylenediamine　by　H2O2.　A　simple　sensitive　colorimetric　senor　was　developed　for　H2O2　by　utilizing　TMB　as　the　substrate　and　BPCN　NSs　as　enzyme　mimetic.　The　linear　relations　between　the　absorbance　and　H2O2　concentration　over　the　range　from　0　to　280　mu　mol　L-1　and　from　280　to　1000　mu　mol　L-1　were　obtained　with　the　limit　of　detection　of　1.0　mu　mol　L-1　according　to　the　3　sigma　rule.　The　colorimetric　sensor　was　applied　for　the　detection　of　H2O2　residue　in　simulated　soaked　foods　with　satisfied　results.　Finally,　the　portable　test　kits　for　H2O2　were　prepared　and　applied　for　the　semi-quantitative　assay　of　H2O2　residues　in　soaked　chicken　feet.