Abstract: In order to study the response of flowers antioxidant enzyme system to the heavy metal Pb-Cd composite stress, it was determined that the POD, CAT and SOD activity changes of different three species of herbaceous flowers garden balsam, peacock grass and short China aster under different Pb-Cd concentration. The results showed that: Under lower concentration Pb-Cd treatment, three kinds of enzyme activity of three kinds of herbaceous flowers increased with treatment concentration increases. When the concentration reached a critical value, it decreased with the concentration increase. The flowers performance was poisoned. The toxic deepened step by step with Pb-Cd concentration increases. Comprehensive to see from the three enzymes change of the three species of herbaceous flowers, three kinds of enzyme activity of garden balsam were highest, peacock grass second, short China aster minimum.