Abstract: Based on the field observation from 1975 through 1993 and textual criticism of the relative literatures, It was concluded that there was no tobacco blue mold (Peronospora tobacina Adam and Peronospora nicotiana Speg) in China in the past or at present. The conclusion was a consensus of scientists in China, United States and others countries. The symptoms, pathogen of tobacco blue mold were systematically introduced and quarantine inspection and control methods were suggested.