Abstract: In order to effectively control tobacco stem rot,the tobacco seedlings infected by the pathogen were collected from float beds.The pathogen of tobacco stem rot was identified as Botrytis cinerea Pers.via pathogenicity test and morphology observation.The results of biological character research indicated that temperature from 22 to 26℃ and pH from 5 to 7 were suitable for its growth.The lethal temperature of spores was 55℃ lasting 20 minutes.