In order to explore the effect and the corresponding physiological mechanismes of UV-C irradiation on browning of fresh-cut apples, both whole and sliced apple were irradiated with UV-C (254 nm) for 5 min before or after processing. The browning index (BI) of slices was immediately measured, while other relevant physiological parameters were evaluated on quick-frozen samples during refrigerated storage. Results indicated that both pre-processing and post-processing UV-C treatment effectively delayed browning of apple slices, nevertheless, post-processing UV-C treatment was more efficient. Browning index (BI) significantly negatively correlated with non-enzymatic capacities, and activities of Catalase (CAT), Ascorbate peroxidase (APX) and Glutathione reductase (GR). BI was positively correlated with the contents of H₂O₂ and Malondialdehyde (MDA). These findings suggested that UV-C treatment delayed browning of apple slices during cold storage by improving the antioxidant system. Post-processing UV-C treatment was more efficient than pre-processing.