Quinclorac acid belongs to quinoline carboxylic acid herbicide. This product is a selective herbicide used to control barnyard grass in rice fields. It belongs to hormone type quinoline carboxylic acid herbicide and is a synthetic hormone inhibitor. The medicament can be quickly absorbed by the germinating seeds, roots, stems and leaves, and rapidly transmitted to the stems and tops, causing weeds to die of poisoning, similar to the symptoms of auxin substances. It can effectively control barnyard grass in direct seeding field, and has good control effect on barnyard grass in 3-5 leaf period.