Abstract: To investigate the microorganisms resulted mildew cigarettes and their biological characteristics, four strains of mold isolated from mildew cigarettes were analyzed by observing the morphological characteristics of the mold and analyzing the sequences of rDNA-ITS, the biological characteristics of the mold were studied as well. The results showed that: 1) The main microorganisms from the mildew affected cigarettes were Cladosporium sphaerospermum, Aspergillus flavus, Penicillium citrinum and Aspergillus oryzae. 2) The four strains in the order of their adaptabilities to different culture mediums, temperatures and humidity were A. flavus > P. citrinum > C. sphaerospermum > A. oryzae, A. flavus > C. sphaerospermum > P. citrinum > A. oryzae and A. flavus > P. citrinum > C. sphaerospermum > A. oryzae, respectively. C. sphaerospermum grew well on culture medium with pH≥ 5; A. flavus grew best at pH of 4.0; P. citrinum had wide adaptability to pH and grew well at pH of 3; A. oryzae grew best at pH of 7. The lethal temperature of C. sphaerospermum, P. citrinum and A. oryzae was 75 ℃ for 10 min, 75 ℃ for 10 min and 65 ℃ for 5 min, respectively; that of A. flavus was 75 ℃ for 10 min or 80 ℃ for 5 min. The rank of the four strains for carbon and nitrogen source utilization were A. flavus > P. citrinum > C. sphaerospermum > A. oryzae. UV had a certain inhibitory effect on the microorganisms of the mold in mildew cigarettes, and the anti-ultraviolet abilities of the four strains were C. sphaerospermum > A. flavus > P. citrinum > A. oryzae.