A phenosafranine (PS) functionalized multiwalled carbon nanotubes (MWNTs) nanocomposite film (PS-MWNTs) modified glassy carbon (GC) electrode was prepared by noncovalent adsorption. The resulting electrode, PS-MWNTs/GC, shows good electrocatalytic activity to the reduction of hydrogen peroxide, and a non-enzyme amperiometric hydrogen peroxide sensor was built. The as-prepared electrode also exhibits excellent electrocatalytic activity to oxygen reduction. By combining the electrocatalytic activity of PS-MWNTs nanocomposite to oxygen reduction with the bioactivity of glucose oxidase (GOx) to glucose oxidation, a glucose biosensor was constructed by further cross-linking GOx on the PS-MWNTs/GC electrode.