Abstract: A pharmacodynamic testing of three herbicides, including 30% picloram · clopyralid, 31% picloram · 2,4 - D and 15% florasulam .fluroxypyr-mepthyl, for controlling Ligularia virgaurea was carried out in Haiyan County of qinghai Province. The results showed that the average control efficacy of 31% picloram · 2,4-D reached up to 80% with the application dosage of I 650 g/hm2, which was higher than the other two herbicides, and it had no phytotoxicity to high quality forage.