Abstract: In order to investigate the relationship between the effect of adjuvants on herbicide solution and their effect on herbicide bioactivity, the physical characteristics of four herbicide adjuvants including Yaoxiaobao, 885, Oil emulsion (N32), Synertrol were measured indoors. The physical characteristics were measured included surface tension, contact angle, dry duration and leaf retention. The methods used were dripping method, contact angle instrument mensuration, drying drop method and ultraviolet spectroscopy instrument mensurationrespectively. The enhancement effect of these adjuvants on sulcotrione controling Amaranthus retroflexus and Echinochloa crus-galli was also measured using pot-planting method in greenhouse. The result showed that Yaoxiaobao could evidently reduced surface tension, decreased contact angle, reduced dry duration and augmented leaf retention, 885 was a little worse, Oil emulsion and Synertrol were worst. The measurement in greenhouse showed that Yaoxiaobao had the best enhencement effect on sulcotrione, 885 took second place. This showed that there is some relationships between the change of physical characteristics in spraying liquid and the enhancement effect on sulcotrione.