Rod-like CeO2 nanoparticles (NPs) were produced by the quick precipitation approach and employed as a catalyzer to increase the chemiluminescence (CL) intensity of the luminol–O2 reaction. The transmission electron microscopy (TEM) images of the CeO2 NPs showed that rod-like particles with the length and diameter about 15 nm and 5 nm, respectively, were produced. Furthermore, pharmaceuticals including oxcarbazepine (OXP) and ascorbic acid (AA) showed an inhibitory effect against the CL intensity such that the more concentration of the pharmaceuticals, the less was the CL intensity. Therefore, the new CeO2 NPs–luminol–O2 CL reaction was developed to determine OXP and AA in the pharmaceutical formulations. It is the rst CL method established for the quanti cation of OXP. The linear dynamic range of this method for OXP was from 6.0×10–7 to 6.0×10–5 mol L−1 and for AA from 1.0×10–6 to 1.0×10–4 mol L−1.