A new sandwich structure nanocomposite of Ag nanoparticles supported on MnO2 modified multiwall carbon nanotubes is synthesized and used for fabricating nonenzymatic H2O2 sensor. The morphology and composition of the nanocomposites are characterized by transmission electron microscope, energy-dispersive X-ray spectrum, X-ray diffraction and Fourier transform infrared spectrum. Electrochemical investigation indicates that the nanocomposites possess an excellent performance toward H2O2. In deaerated buffer solutions, the sensor could detect H2O2 in a linear range of 5.0 mu M to 10.4 mM with a correlation coefficient of 0.9993, a sensitivity of 82.5 mu A mM(-1) cm(-2), a detection limit of 1.7 mu M at a signal-to-noise ratio of 3, and a response time of 2 s. Additionally, the sensor exhibits long-term stability, good reproducibility and anti-interference. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.