Nanozymes, as a robust alternative to natural enzyme, usually suffer from unsatisfactory catalytic efficiency and limited modulating flexibility. Herein, we proposed a novel strategy to conquer these disadvantages relying on the facet-selective response of external trigger molecule which boosts the oxidase-like catalysis of nanoceria. Results indicate that the trigger molecule (i.e., sulfate ion) prefers to bind to the rod-like nanoceria (on its unique {1 1 0} facets) rather than nanopolyhedra or nanocubes. Sulfate ion-treated CeO2 nanorods (SO42- /CeO2 NRs) became modulatable oxidase mimetics of high efficiency, and the catalytic efficiency (k(cat)/K-m) of SO42- /CeO2 NRs improved by nearly 20-fold (versus that of the naked CeO2 NRs) for 3,3 ',5,5 '-tetramethylbenzidine (TMB) oxidation. This modulating strategy, together with the mechanism behind, is finally applied to develop colorimetric biosensors, which paves the way for embedding the system in biological and environmental networks.