Abstract: In order to understand the mechanism of corn to stalk rot caused by Fusarium graminearum, changes of PAL activity, POD activity and lignin in the pith tissue of corn stalk of resistant variety Shaandan 931 and susceptible variety Xinong 11 inoculated with Fusarium graminearum were mainly studied. After inoculation, PAL activity of Shaandan 931 was strong and increased rapidly and showed two peaks, while that of Xinong 11 was comparely weak and increased slowly and showed only one peak. Both Shaandan 931 and Xinong 11 showed one POD activity peak after inoculation. But the peak value of POD activity of Shaandan 931 was higher than that of Xinong 11 and the duration of high POD activity of Shaandan 931 lasted longer than that of Xinong 11. It was clarified that the lignin produced originally in corn plant had no relation to resistance of corn to stalk rot. It was the induced lignin produced by corn plant after inoculation of F. graminearum that showed contribution to the resistance only. Corn plant could produce some substances that could suppress the growth of F. graminearum when it was infected by F. graminearum.