Pd-modified N-doped TiO2 nanoparticles were prepared by the sol-gel method. The X-ray diffraction (XRD) pattern indicated that the pure anatase TiO2 has been obtained. Transmission electron microscope (TEM) was used to observe the micro-morphology of the nanoparticles. The average size of the particles was 8.04 nm. The N2 adsorption isotherm of the resulted nanoparticles was the type IV with a H1 type hysteresis loop. The specific surface area was 145.2 m2 g(-1) and the average diameter of adsorption was 4.178 nm. These Pd-modified N-doped TiO2 nanoparticles were applied onto the surface of glass carbon electrode (GCE), and its electro-catalytic activity was tested by cyclic voltammetry (CV). The reduction peak currents showed a linear response to the dissolved oxygen (DO) concentrations ranging from 0.6 mg L(-1) to 7.2 mg L(-1) on the Pd-N-TiO2/ GCE. The linear regression equation was y = 3E - 6x + 1E-5 (R = 0.9909). The detection limit was 0.22 mg L(-1.) The result indicated that the Pd-N-TiO2 possessed a good electro-catalytic activity.