Abstract: The pathogen and prevention of soft rot disease on Paris polyphylla var. chinensis is studied to cultivate this important Chinese medicinal herb. Field investigation was conducted to observe the symptom on the sick plants of P. polyphylla var. chinensis, and tissue separation was conducted to separate and purify the pathogen, and then the pathogen was identified through microscopic observation. The pathogenic sites on soft rot disease on P. polyphylla var. chinensis were stem, leaf and flower, the plant bent and seriously rotted after disease attack. Early stem lesion was oval and water-soaked, and then black dots appeared. The onset of the disease on leaf was petiole, at first petiole was covered by white mold, and the whole leaf was water-soaked later. The onset of the disease on flower was pedicel and then outer perianth lobe, and sign and symptom were similar to those on leaves. Pathogen hyphae without diaphragm developed well, was consisted of branches, creeping silk and rhizoid. Sporangiophore upright stood, and the single spherical sporangium was on the top of sporangiophore. The pathogen of soft rot disease on P. polyphylla var. chinensis was Rhizopus stolonifer. Ventilation and drainage were necessary after rain, and carbendazim and thiophanate methyl were effective pesticides for prevention and cure the soft rot disease on P. polyphylla var. chinensis.