Experiments included 17 treatments of Nitrogen fertilizer: 16 treatments of different nitrogen dose and 1 treatment of no applying nitrogen on 2 hybrid maize varieties of LVN 14 and LVN99 in Spring 2011 and 2012 in Thai Nguyen. Research results showed that: Growing time, number of root collapsed plants, number of stem broken plants and pest infestation levels of LVN 14 and LVN99 varieties increased proportionally to the content of nitrogen. Actual yield of LVN 14 was equivalent to LVN99 and proportionally increased to nitrogen applying at the period of 4-5 leaves (no applying nitrogen at the period of 8-9 leaves. Treatments of applying 0-25 kg N/ha in the period of 4-5 leaves had yield that proportionally increased to the amount of nitrogen applied during the period of 8-9 leaves. Treatments of applying 50-75 kg N/ha in the period of 4-5 leaves had the highest yield at the period of 8-9 leaves which applied nitrogen of 50 kg N/ha and 25 kg N/ha, respectively.