Take fennel seeds from Inner Mongolia as the materials.By using the method of nutrient solution culture,effect of different nitrogen forms (NO3--N/NH4+-N ratio was 50/50,30/70,70/30,100/0,0/100) on plant growth and components of essential oil in fennel were studied on the basis of examination of the Japanese Garden formula.The results showed that NO3--N/NH4+-N ratio affected the plant growth of fennel significantly,and there was the best for plant growth of fennel with the ratio of NO3--N/NH4+-N at 100/0,and the growth of fennel plant with the ratio of NO3--N/NH4+-N at 70/30 was lower than that with the ratio of NO3--N/NH4+-N at 100/0,however,the plant growth of fennel in the both treatments was better than examination of the Japanese Garden formula.