Abstract: Under dry-raising condition in the paddy fields, an experiment was conducted to determine the differences in weed suppression ability between allelopathic rice “PI312777” and its counterpart “Lemont”. The results show much higher inhibitory effect of “PI312777” than “Lemont” seedlings on weeds under the 2 soil water conditions. The absolute value of weed suppression index for “PI312777” is more than 0.5, and the reverse is the case for “Lemont”. Further analysis suggests that dry stress increases weed suppression ability of the two rice varieties, and the degree of increase for allelopathic rice “PI312777” is higher than its counterpart “Lemont”. With regard to weed biomass, weed suppression effect of “PI312777” can be described as allelopathic inhibitory, which is enhanced by moderate dry stress. Rice has different obstruction ability for different weed species. Allelopathic rice “PI312777” has greater control ability for broadleaf weeds in summer rice fields, and for barnyard grass (Echinochloa crusgalli) under water deficiency stress.