The invention discloses a pseudo-ginseng WRKY transcription factor gene PnWRKY9 and the application thereof. The nucleotide sequence of the PnWRKY9 gene is as shown in SEQ ID NO: 1, and the PnWRKY9 gene encodes a WRKY transcription factor; according to the application, molecular biology and functional genomics related technical researches prove that the PnWRKY9 gene has the function of improving the fungal disease resistance of plants, the antifungal gene PnWRKY9 is constructed on a plant expression vector and transferred into tobacco for overexpression, and the transgenic tobacco plant has very strong in-vitro antifungal activity; according to the present invention, the PnWRKY9 overexpressed transgenic tobacco has the significant inhibition effect on the growth of Alternaria Compacta, Fusarium solani, and Nigrospora oryzae, and the PnWRKY9 overexpressed transgenic tobacco has the significant inhibition effect on the growth of the Alternaria Compacta, the Fusarium solani, and the Nigrospora oryzae, such that the PnWRKY9 overexpressed transgenic tobacco has the significant inhibition effect on the growth of the Nigrospora oryzae,.