Abstract: Comparative study of biological characteristics between Alternaria alternata and Alternaria tabacina were carried out. The results showed that the optimal growth temperature for Alternaria alternata and Alternaria tabacina were 2530 ℃ and 2025 ℃ respectively; A. alternata grew better than A. tabacina at pH 69; glucose and sugar utilization of A. alternata was higher than that of A. tabacina; the same results were got for the use of acmonium nitrate, acmonium sulfate and casein by Alternaria alternata and Alternaria tabacina. Both organisms showed the highest utilization of casein, followed by acmonium nitrate and acmonium sulfate. There were significant differences in mycelia growth of Alternaria alternata and Alternaria tabacina on potato agar, glucose agar and sugar agar respectively, while no differences existed between that of Alternaria alternata and Alternaria tabacina on cornmeal agar. Iprodione and Mancozeb totally inhibited the growth of A. alternata and A. tabacina. No difference existed in the inhibitive effects of chlorothalonil or stroby on A. alternata and A. tabacina while Topsin-M showed better inhibition on the mycelia of A. tabacina than that of A. alternata. .