Abstract: Some biological characters and its inheritance of the causal organism of cotton boll blight in Anhui were studied in vitro. The results showed that the growth-rate and pathogenicity to cotton seedlings of all tested strains in different regions displayed obvious difference, and even in the same region. And it also showed that the inheritance of the growth-rate and pathogenicity to cotton seedlings of XC-6 could not be inherited steadily in zoospore progenies and oospore progeny, but the colony morphology and homothallic character of XC-6 could inherited steadily in both asexual and sexual progenies, which suggested that the inheritance and variation of the above characters might be related to long-selfing and hybridization in species.