Saliva is an easily collected body fluid and has simple composition. Some drugs concentrations in saliva can reflect their blood level. This paper analyzes the mechanisms of drug transfer from blood into saliva and the influencing factors, reviews the methods of sample collection, preparation, analysis of the abused drugs in saliva, and the relationship between abused drugs content in saliva and in blood. We believe that saliva is a valuable sample in clinic and forensic medicine. It is important in forensic science field to estimate abused drugs concentrations in blood by via their saliva concentrations.