Reasonable sensor construction for precisely realtime detecting H 2 O 2 produced from living cells has always been of great significance and challenges. Due to the excellent catalytic efficiency and unparalleled peroxidase-like activity, single-atomic catalysts with Fe-N x active sites show great potential in H 2 O 2 detection. These special atomic active sites make it easier for the Fenton reaction to occur, which provides basic support for H 2 O 2 sensors. Their application in the in situ real-time detection of H 2 O 2 has important market prospects. Herein, single-atomic Fe catalysts with distorted graphitic carbon are obtained through a simpler preparation method. A precursor hemin@zeolitic imidazolate framework-8 (hemin@ZIF-8) is calcined at a high temperature and carbonized to get the nitrogen-carbon codoped Fe single atoms (Fe SAs-N/C) and then successfully prepare a H 2 O 2 electrochemical sensor by modifying it on a glassy carbon electrode (GCE). Its peroxidase activity is calculated by enzymatic kinetics, which shows a better peroxidase activity compared with horseradish peroxidase and other reported single-atom (SA) materials. Moreover, the electrocatalytic kinetics is explained by Laviron calculation, which more directly confirms that it has a faster electron transfer rate. Importantly, Fe SAs-N/C@GCE has a wider linear range than sensors combined with other SA materials and a low detection limit of 0.34 μM. It is an attractive design of H 2 O 2 sensors and single-atomic catalysts with superior substrate affinity that are novel alternatives to natural enzymes.