Four tomato cultivars used as materials, the change of superoxide dismutase（SOD）, peroxidase（POD）and phenylalanine ammonia-lyase（PAL） activities in tomato seedling leaves under drought stress simulated by poly-ethylene glycol were studied. The results showed that four tomato cultivars had the same tendency. SOD activities in-creased significantly, reached a maximum at 48 h, then, decreased. POD activities increased quickly, reached a max-imum at 24 h, and Yazhi had the highest increase which activities of treatment group was 4.13 times of control group.Then, the activities decreased quickly, after reaching a low value at 48 h, it increased to some extent. In the wholeprogress the POD activities of treatment group were higher than the control group. The PAL activities of Yazhi andMoneymaker in treatment group increased at first, then, decreased. The activities of Caidu No. 5 and Super 908 in-creased slowly, and the PAL activities of treatment group were higher than the control. The orders of stress coeffi-cient obtained from SOD activity, POD activity and PAL activity respectively were identical. The stress coefficientranked from high to low was Yazhi, Moneymaker, Caidu No. 5, Super 908, indicating that Yazhi responded activelyand had relatively strong ability of removing reactive oxygen, repairing the damage and adapting to the drought stress.