Eucalyptus urophylla Blade MLA clone (MLA) was a difficult to root species. E. urophylla Blade U 6 clone (U 6) and E. ABL 12 W 5 clone (W 5) were relatively easy to root species. The activity of polyphenol oxidase (PPO) in MLA was lower than that in U 6 and W 5. After the cuttings of Eucalyptus were treated with naphthylacetic acid (NAA), the activities of PPO increased regularly in different stages of rooting. The relationship between the oxidase and rooting of Eucalyptus cuttings was discussed.