Bioassay results of the study indicated that Toxins from Pseudocercospora oxalidis had tox- icity on the leaves of Oxalis corymbosa DC.The optimal cultural conditions for the production of phytotoxin produced by Pseudocercospora oxalidis were temperature 25℃,pH6,cultured period 15~18days.Furthermore,the productionof phytotoxin favored darkness and enough swing of the ferment liq- uid.