Ruminal methane (CH_4) emission not only causes energy waste of diets, but also contributes to global warming. The methanogens mainly utilize carbon dioxide (CO_2) to produce CH_4 in rumen of ruminants. Methyl coenzyme M reductase takes a part in the last step of reduction pathway of CO_2 in the process of CH_4 synthesis, while 3-nitrooxypropanol (3-NOP) has the similar structure with methyl coenzyme M, which can combine with coenzyme B, and then reduce the combination between methyl coenzyme M and coenzyme B to produce CH_4. Thus, 3-NOP can effectively reduce the ruminal CH_4 production. This paper reviewed the inhibitory mechanism of 3-NOP on ruminal CH_4 emission, as well as the effects on performance of ruminants.