The objective of this trial was to examine the effect of applying sodium dehydroacetate on the fermentation of blue-grass silage. Whole plant blue-grass was ensiled in laboratory bags after treated with sodium dehydroacetate at three rates, 0.05% of fresh weight (SD1), 0.1% of fresh weight (SD2), and 0.2% of fresh weight (SD3), LuproMix NC as a positive control (0.35% of fresh weight), or no additive (untreated). The each SD treatment had lower the final pH than the untreated (P<0.05), but the difference was not significant compared with positive control (P>0.05). All the three SD treatments had lower ammonia nitrogen (as % total nitrogen) than the untreated (P<0.05), and the significant differences in ammonia nitrogen between SD3 treatment and LuproMix treatment were observed (P<0.05). Lactic acid bacteria count (cfu/g) after ensiling were unaffected by application rates of SD, but yeast/mold counts were lower for SD treatments than both controls. The SD3 treatment had the greatest the lactic acid concentration and ratio of lactic acid:acetic acid, while LuproMix had the lowest the lactic acid concentration and the ratio. Except for SD3, there were no differences in the lactic acid concentration among all the treatments. Thus, it is concluded that blue-grass silage quality can be improved by using SD3 as a antifungal additive to reduce the growth of detrimental bacteria.