Abstract: The influence of organosilicone adjuvant(OSA) on deposition and bioactivity of glyphosate on alligator weed(Alternanthera philoxeroides) were conducted. The deposition of glyphosate that treated with the addition of OSA(0.35 g/L) and sprayed over 632.5 L/ha decreased more than that without OSA.The maximum deposition of glyphosate solution (MRG) on alligator weed leaves was 0.61-0.63 μ L/cm2,however,the MRG was 0.50-0.54 μ L/cm2 when treated with the addition of OSA.After glyphosate 33.7 and 67.4 μ g/plant treatment,the regrowth shoots reduction for treatment with addition of OSA were increased by 8.89% and 14.83%,respectively,compared to that without OSA.For artificial raining treatment 1 h after glyphosate(199.3 g a.i./ha) application,the bioactivity of glyphosate treatments with OSA was increased by 20.5% compared to that in absence of OSA.The results indicated that the translocation and rain fastness of glyphosate in alligator weed were improved when treated with addition of organosilicone adjuvant,but the maximum deposition of glyphosate solution on the weed would be decreased in condition of high spray volume.