The work aims to clarify the oxygen-blocking mechanism of oxygen scavengers in oxygen-blocking films and their influence on the physical and chemical properties of the films. Three commercially available oxygen scavengers (CoFresh 162, valOR 115J, and Amosorb 4020E) were added to PET substrates to prepare oxygen-blocking films. The oxygen absorption capacity of the films was tested by immersing them in water, and their oxygen transmission rate was characterized with an oxygen transmission rate testing system. The haze, light transmittance, and microstructure of phase separation were characterized with a haze meter and a scanning electron microscopy (SEM). The oxygen-blocking films containing the three different oxygen scavengers could actively and effectively absorb dissolved oxygen in water, with the oxygen absorption amounts reaching 9.83, 9.80, and 8.89 cm3/g after 30 days, respectively. The addition of oxygen scavengers could significantly enhance the active oxygen-blocking performance of the films, but the effect of the scavengers would gradually decrease over time. The haze values of the three oxygen-blocking films containing 5% oxygen scavengers were 5.5%, 6.8%, and 20.7%, respectively. The addition of oxygen scavengers would reduce the mechanical properties of the films. The concept of active oxygen-blocking performance based on oxygen transmission rate testing is adopted in the study of the physical and chemical properties of oxygen scavengers to evaluate the oxygen absorption kinetics of the scavengers. The evaluation results indicate that CoFresh 162 has the best active oxygen absorption performance, oxygen-blocking performance, and the lowest haze value, and can be used to prepare single-layer oxygen-blocking films/bottles, suitable for food packaging materials.