Abstract: In order to confirm pathogenicity differentiation within Sclerotinia sclerotiorum groups, ninety-three isolates of Sclerotinia sclerotiorum isolated from soybean and sunflower in different regions of Heilongjiang Province were tested for their pathogenicity to Fengkuiza NO1 variety by the method of placing the mycelia plugs on the excised leaves. The results of inoculation on excised leaves of Fengkuiza NO1 showed that 79 isolates had pathogenicity although the lesion sizes ranged from 0.2cm to 5.3cm in different isolates. However, no pathogenicity was found in fourteen isolates. The number of moderate pathogenicity isolates of Sclerotinia sclerotiorum were more than others and 66.7% proportion in the pathogen population. Furthermore, the extremely significant differences of pathogenicity were found among isolates even derived from the same region and the same field. The results indicated that the phenomenon of pathogenicity differentiation was existed among isolates, which was no significant relationship to geographical location and host origin of the isolates.