Abstract: Aspergillus cristatus is dominant fungus in Chinese Fuzhuan brick tea，and can undergoes sexual and asexual stages under condition of high and low osmotic pressure，thus is a well suited for studies of the fungal sporulation.flbD in filamentous fungi is a vital regulator of asexual development，thus function of flbD in Aspergillus cristatus was studied.flbD was deleted by gene replacement，phynotype difference between the wild type with mutant were observed under different conditions，these results were as follow：number of conidia of the wild type was 4.7 times that of the knockout strain；growth rate of hyphae had no significantly difference between mutant with wild type strain.The mutant could form aerial hyphae with“cotton”；meanwhile，conidiophores of ΔflbD were latter than that of wild type under high osmotic pressure.Function of flbD in the asexual stage of Aspergillus cristatus was detected by gene replacement，results indicated that asexual spore were obviously decreased in the mutant，thus flbD positive regulated asexual process in Aspergillus cristatus.It is significant for the study of asexual development in fungi.