For the first time, functional Corrole molecules modified iron oxide (Fe3O4) magnetic nanoparticles (MNPs) were prepared by a facile two-step method. The Corrole-Fe3O4 nanocomposites exhibited a higher peroxidase-like activity than that of pure Fe3O4 nanoparticles, and accelerated the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) with the help of hydrogen peroxide (H2O2) only in 5 min, attributing to hydroxyl radicals (·OH) generated in the process of oxidation of TMB. Kinetic analysis showed that the catalytic behaviors followed the typical Michaelis-Menten kinetics. Additionally, Corrole-Fe3O4 exhibits several advantages including low cost, easy separation, facile fabrication, and high catalytic efficiency. Based on the catalytic activity of Corrole-Fe3O4 nanocomposites, a simple, sensitive, and selective colorimetric biosensor for H2O2 and glucose determination was successfully designed. The linear relationships of absorbance of oxidized TMB at 652 nm with H2O2 or glucose concentration were obtained from 10 μM to 100 μM with a detection limit of 3.6 μM and 4 μM to 40 μM with the detection limit as low as 2.46 μM, respectively. The results demonstrate that the Corrole-Fe3O4 nanocomposites have potential applications in bioanalysis and biodetection.