Abstract: Radiolabeled fomesafen was used to investigate the effects of spray adjuvants ABS(sodium dodecyl benzene sulfonate) and JFC(penetrating agent JFC) on the foliar uptake and fomesafen efficacy on Amaranthus retroflexus. Results indicated that compare to fomesafen applied alone the addition of JFC at 2 g/L increased 1.4-fold areas of uptake, 3.2-fold amount of uptake and 28.5% efficacy of fomesafen; the addition of ABS at 2 g/L increased 1.3-fold areas of uptake, a fold amount of uptake and 19.2% efficacy of fomesafen for A. retroflexus. Not only could JFC increase the areas of uptake, but also it enhanced the activity per unit area. The activity was enhanced to 75.7% by JFC at 2 g/L on A. retroflexus. Basically, ABS could only increase the areas of uptake, but did not enhance the activity.