In this work, we demonstrate the fabrication of polypyrrole (PPy) decorated TiO2/Fe2O3 (TiO2/Fe2O3/PPy) composite nanofibers with a core-shell structure as an artificial enzyme system with a high peroxidase-like activity. The TiO2/Fe2O3 nanofibers with a diameter in the range of 40-150 nm and a relatively narrow distribution of diameter size are prepared via an electrospinning technique and followed by a calcination process. Then we are able to in situ polymerize a layer of PPy on the surface of the TiO2/Fe2O3 nanofibers by using Fe2O3 on the surface of nanofibers as an oxidant. The resulting ternary TiO2/Fe2O3/PPy composite nanofibers exhibit an enhanced peroxidase-like activity toward the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) in the presence of H2O2 over independent TiO2, Fe2O3 and TiO2/Fe2O3 composite nanofibers due to the synergistic effect. On the basis of the high peroxidase-like activity, a simple approach for the colorimetric detection of H2O2 with a detection limit of 2.4 mu M and a linear detection range from 2 to 50 mu M has been proposed. This work offers a new way for manipulating the enzyme-like performance of electrospun nanofibers for a wide range of potential applications in biosensing and environmental monitoring.