4-Hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27, HPPD) is an important enzyme in the catabolism oftyrosine, which converts 4-hydroxyphenylpyruvate (HPPA) into homogentisate (HGA).In plants, HGA is an important precursor for the biosynthesis of tocopherol and plastoquinone, two compounds crucial for the normal growth of plants.When HPPD is inhibited, the plant will be severely damaged by sunlight, becoming bleached and eventually undergoing necrosis and death.[1-3] Inhibition of HPPD is one of the most promising modes of action of herbicides.It is widely reported that quinazoline-2,4-dione is an important chemical scaffolds, because these derivatives often posses a variety of biological activities, such as antitumor, anti-inflammatory, antidiabetic, anti-infective, and antiobesity properties.[4] Although the derivatives of quinazoline-2,4-dione are extensively studied in medical chemistry,the research of them in agrochemicals is very scare, especially the herbicidal activity of them need to be further explored.To explore the herbicidal activity of quinazoline-2,4-dione derivatives, and study their HPPD-inhibiting activity, we designed and synthesized a series of novel triketone-containing quinazoline-2,4-diones.The in vitro tests indicated that many of the newly synthesized compounds displayed good AtHPPD inhibitory activity with Ki values ranging from 0.005 to 0.668 μM.In addition, the greenhouse experiments indicated that most of the synthesized compounds showed good or excellent herbicidal activity against broadleaf and monocotyledonous weeds at the dosages of 37.5-150 g ai/ha.Most promisingly, some compounds showed significantly improved crop selectivity compared with mesotrione.