Nitric oxide synthase (NOS) is an important part of nitric oxide (NO) research in the fields of biology and medicine. In recent years, there is a rapid development in the researches of the nature and molecular characteristics of NOS, ever in some aspects of molecular genetics of NOS. Researches showed that to intervene in some processes of NOS-NO pathway, such as activation of the enzyme, synthesis, release and transportation of NO, and even genes related to encoding and expressing enzyme will provide new clues and methods for managing some clinic problems.