Abstract: Wilt diseases of two cultivated medicinal plants in Guangdong province,the common an-drographis (Andrographis paniculata)wilt ,and black pepper (Piper nigrum) wilt ,were investigated and identified. Formae specialis of Fusarium oxysporum were studied . According to the tests morphology , cultural characters and pathogenecity, the wilt disease of common andrographis was caused by Fusarium oiysporum Schl. f. sp. andrographis K. X. Zhou & P. K. Chi,f. sp. nov. .for which impregnated inoculation method was available; the wilt of black pepper was caused by Fusarium oxysporum Schl. f. sp. piperis K. S. Zhou & P. K Chi f. sp. nov. that has close relation to root knot nematode disease. Both of them were formae specialis of Fusarium oxysporum.