Abstract: The objective is to evaluate the inhibitory effect and the stability of an allelopathic rice male sterile line‘N57S’on barnyard grass (Echinochloa crus-galli L. Beauv) in filed, and explore the prospect of‘N57S’ in rice breeding.‘PI312777’and‘allelopathic rice 3’were used as control. Three sowing dates were set up. Five kinds of weed suppression traits and their stability were analyzed. The results showed that,‘N57S’ performed strong weed suppression ability against barnyard grass in three sowing dates. The average inhibition rate of‘N57S’at filling stage in three sowing dates was between‘PI312777’and‘allelopathic rice 3’, showing no significant difference. The other four weed suppression traits also showed no significant difference compared with the control in three sowing dates. The stability of the inhibition rate of filling stage of‘N57S’ and the average plant height and the dry weight per plant of associated barnyard grass were better than those of the two controls. The stability of the inhibition rate of filling stage of‘N57S’was the best among the five weed suppression traits, and its coefficient of variability was just 4.51%. And then the inhibition rate of filling stage of‘N57S’can be regarded as a standard to evaluate the allelopathy of‘N57S’preliminarily. The correlation analysis showed that the total inhibitory effect of allelopathic rice on barnyard grass was decided by the allelopathy effect and competition effect jointly. And the germination of barnyard grass was mainly suppressed by the allelopathy effect, while the survival rate and the biomass accumulation of the survival barnyard grass was mainly inhibited by the competition effect, but the correlation between them was not statistically significant.‘N57S’was an excellent allelopathic rice material which performed strong inhibitory ability on barnyard grass and had some stable weed suppression traits in field, owning brilliant prospect in application and study.