A facile enzyme-free hydrogen peroxide electrochemical sensor was fabricated based on multilayer ultrathin film containing Naphthol green B anions (NGB) and exfoliated nanosheets of Co-Al layered double hydroxide (LDH) via layer-by-layer self-assembly technique. The X-ray diffraction pattern indicates the superlattice structure of the film with repeating distance of 4.15 nm: SEM and AFM images show that the film surface is continuous and uniform. The electrochemical behavior of the ultrathin film was studied by cyclic voltammetry and electrochemical impedance spectroscopy. The ultrathin film modified electrode shows a fast direct electron transfer for the Co2+/Co3+ redox couple with Delta E = 14 mV in 0.1 M NaOH solution. Furthermore, the modified electrode displays a significant electrocatalytic performance for H2O2 with Michaelis-Menten constant K-M(app) = 169.3 mu M. The anodic peak current increased linearly with the concentration of H2O2 from 8.0 x 10(-6) to 1.8 x 10(-4) M with a low detection limit of 9.0 x 10(-7) M. The NGB/LDH ultrathin film was demonstrated as a feasible electrochemical sensor for detection of H2O2 with rapid response, high stability, good reproducibility and excellent selectivity. (C) 2010 Elsevier Ltd. All rights reserved.