Nanozymes, as substitutes for natural enzymes, have been used to construct some fast cheap sensing platforms by virtue of the high catalytic activity. Herein, we firstly study the peroxidase-like activity of CeO2/Co3O4@N-doped hollow carbon microspheres as nanozymes. In the presence of H2O2, CeO2/Co3O4@NCH exhibits high peroxidase-like activity evaluated by the catalytic oxidation of the chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxTMB visually in 1min. The larger surface area, pore-like structure, and oxygen vacancies contribute to the enhanced peroxidase-like activity of CeO2/Co3O4@NCH. The active species •O2- is detected during the catalytic process. Thus, based on the excellent peroxidase-like activity of CeO2/Co3O4@NCH, a facile and effective biosensor is fabricated for sensitive and selective determination of H2O2 and quercetin, respectively. CeO2/Co3O4@NCH shows high affinity towards H2O2 (Km = 4.001mM) and TMB (Km = 0.086mM). The detection limit of H2O2 and quercetin is as low as 0.086mM and 1.19μM (3σ/slope), respectively. This work remarkably extends the utilization of CeO2/Co3O4@NCH in designing a colorimetric sensing platform related to biosensing, food, and environmental monitoring. A fast colorimetric sensing platform for quercetin based on the excellent peroxidase-like activity of CeO2/Co3O4@NCH.