Abstract: Field trail was carried out to investigate the effects of potassium chloride (KCl) on phenolic metabolism of corn inoculated by Fusarium graminearum. The result showed that corn took up more K, when inoculated with pathogen. Application of KCl improved the induced activity of Phenylalanine ammonialyase (PAL)，accelerated the Polyphenol oxidase (PPO) activity, raised Peroxidase (POD) activity, which peaked in second pith above ground. Moreover, applying K could increase not only the inherent lignin content but also the induced lignin content and phenol content after inoculation. It was indicated that potassium could enhance resistance to stalk rot of corn through regulation of phenolic metabolism and thereafter secondary metabolism.