Abstract: -In order to clarify the synergistic effect of 3% lecithin + vitamin E (AnnGro^®) on glyphosate and its absorption and conduction characteristics in plants. Alternanthera philoxeroides was taken as experimental material. The ED₅₀ and ED₉₀ values of AnnGro^® mixed with two glyphosate-isopropylammonium (FD and RD) were calculated by bioassay, and the surface tension, and the contact angle of the liquid with the leaf surface were tested. The absorption and conduction of ¹⁴C-glyphosate in A. philoxeroides were measured by isotope tracer technique. The results showed that A. philoxeroides died one day earlier when treated by two herbicides mixed with AnnGro^® than by the herbicides alone. ED₅₀ and ED₉₀ values were significantly decreased by 34.9%, 21.4%, and 35.9%, 23.3% respectively. The surface tension and the contact angle between the liquid and the leaf were significantly decreased. Four days after treatments, the total absorption amount of ¹⁴C-glyphosate, the total conduction amount in plant and the downward conduction amount of ¹⁴C-glyphosate in the treatment of ¹⁴C-glyphosate + AnnGro^® were 2.33, 2.34 and 2.36 times compared with the treatment of ¹⁴C-glyphosate only. In conclusion, AnnGro^® improved the control efficacy of glyphosate on A. philoxeroides by increasing the absorption and the conduction in A. philoxeroides.