Oxygen vacancy is one intrinsic defect in metal oxide materials. Interestingly, we herein found that the surface oxygen vacancy can significantly enhance the catalytic activity of Co 3 O 4 nanowires in the luminol-H 2 O 2 chemiluminescence (CL) reaction. 0.1 ng/mL Co 3 O 4 nanowires containing 51.3% surface oxygen vacancies possessed ca. 2.5-fold catalytic activity of free Co 2+ (the best metal ionic catalyst for the luminol-H 2 O 2 CL reaction). The superior catalytic efficiency is attributed to the enhanced adsorption of H 2 O 2 by surface oxygen vacancies, which in turn accelerates the cleavage of O-O bonds and generates • OH radicals. More importantly, the surface oxygen vacancy-rich Co 3 O 4 nanowires retained about 90% catalytic activity after modification with antibodies. The surface oxygen vacancy-rich Co 3 O 4 nanowires were used to label the secondary antibody, and one sandwich-type CL immunoassay of carcinoembryonic antigen was established. The detection limit was 0.3 ng/mL with a linear range of 1-10 ng/mL. This proof-of-concept work proves that surface oxygen vacancy-rich Co 3 O 4 nanowires are suitable for labeling biomolecules in CL bioanalysis and biosensing.