\[Abstract\]Recently increasing functions of nitric oxide (NO) has been discovered. Researchers around the world have reported that NO plays an important role in the anti-microbial infection; however, more recent studies have found that NO also protect the growth of microorganisms, for example, it can facilitate drug resistance of bacteria and it can protect microorganisms from oxidative stress and pressure. This paper reviews both positive and negative roles of NO on microbial growth and the related mechanisms.