Under three level of applications of nitrogen fertilizer, six Japanese differential strains of Piricularia oryzae were used to inoculate twelve Japanese singal-gene differential varieties respectively. According to the changes of type and number of lesion, the effect of different applications of nitrogen fertilizer on vertical resistance of rice varieties was tested. The result indicates that with the increase of applications of nitrogen fertilizer, the number of susceptible type which increased lesions, in the number of accounted for 6.9% the types of lesions changing from resistance to susceptibility accounts for 23.6% of total, of which, 13.9% became susceptible ones in mid-lever application of nitrogen fertilizer, and 9.7% in high-level application of nitrogen fertilizer. Thus it can be seen that the vertical resistance of some rice varieties is affected by applications of nitrogen fertilizer, and some of them are more sensitive to nitrogen fertilizer.