Polycyclic aromatic hydrocarbons (PAHs) are widespread in nature because of several polluting anthropogenic activities. They have been recognized as a potential health risk due to their intrinsic chemical stability, high recalcitrance to different types of degradation and high toxicity to living organisms. Soil enzymes, being in intimate contact with the soil's environment and very sensitive to any ecosystem perturbation, are well suited for assessing the impact of pollution on the soil quality. The aim of this trial was to quantify the responses of soil enzyme activity during the phytoremediation of PAHs impacted soil. Four tree species including Cinnamomum camphora, Magnolia grandiflora, Koelreuteria bipinnata, Liriodendron chinense, from subtropical China, were selected and planted separately in the pots in which soils were treated with diesel oil to three concentration levels of PAHs(L1﹤L2﹤L3). Phosphatase, polyphenol oxidase and hydrogen peroxide activity were evaluated at 0, 3, 6, 9 and 12 months after the PAHs contamination. The resulted showed that the inhibition rates of polyphenol oxidase activity ranged from -94.98% to 16.29%, the inhibition rates of hydrogen peroxide activity ranged from -76.71% to 13.19%, and the inhibition rates of phosphatase activity ranged from -49.62% to 56.38%. Enzymatic activity in PAHs contaminated soils were also affected by different tree species. Analysis of variance indicated that there was a significant difference of hydrogen peroxide activity between different PAHs levels and there were a significant difference of 3 enzyme activities between different times, but all 3 enzyme activities were not significant between interactions of different trees and PAHs levels and between interactions of different times and PAHs levels. Two principal components were extracted from the principal component analysis and their cumulative contribution of variance accounted for 94.19%. The variance contribution rate of PC1 and PC2 were 87.61% and 6.58%, respectively. The correlation coefficients between main substrates and PC1 or PC2 indicated that enzymatic activity was influenced by PAHs and trees together, but the such influence from PAHs contamination was higher than that from the trees. Meanwhile, the principal component analysis also showed the polyphenol oxidase and phosphatase activities impacted by the PAHs and trees were higher than the hydrogen peroxide activity.