Abstract: According to the pathological anatomical observation to the grains infected by Ustilaginoidea virens from the field, there were the integrated floral organ including stamen and pistil, which were isolated from the infected grains without forming yellow chlamydospore. The integrated ovaries, which were green and not obviously enlarged because of grain filling, were isolated from the typical infected grains with lots of yellow chlamydospore. Some male\|sterile rice lines were infected by this fungus and resulted in the typical symptoms. It was proposed that the fungus Ustilaginoidea virens infected the pistil before the flowering and absorbed nutrition from the ovary to develop the smut ball．

Key words: rice false smut(Ustilaginoidea virens), rice false smut ball, infect period, infect position