Abstract: In order to explore the effects of different nitrogen levels on the growth, root and blade of Grevillea robusta and Jacarand mimosifolia, the exponential fertilization method was used on two species seedlings fertilization experiment. The result showed that: (1) Growth performance and biomass changes of Grevillea robusta and Jacaranda mimosifolia that had been treated with exponential fertilization were significantly related to nitrogen supply levels. With the change of nitrogen application, it exhibited a different degree at each growth indexes of the two species seedlings affected by nitrogen. (2) Except the bifurcation number of root, effects of different concentration nitrogen treatments on the root of Grevillea robusta and Jacaranda mimosifolia had not significant difference. With the nitrogen in-taken, the root of different tree seedling species had different performance. Root volume, root surface-area and root projected area presented similar law, and the changing law of crossing number kept consistent with the length of root-tip, and the average diameter and bifurcation number showed increasing firstly and then reducing and increasing finally. Root volume, root surface-area, root projected area and the length of root-tip of Jacaranda mimosifolia were similar, but the root number and bifurcation number were quite different. (3)Effects of different concentration nitrogen treatments on the leaf of Grevillea robusta and the leaf of Jacaranda mimosifolia had not significant difference. Effects of the leaf of the two seedlings treated had different performance. Leaf area, blade area and comparison of blade length to blade width of Grevillea robusta presented a similar changing trend, and the changing trend of limb circumference kept consistent with perforation numbers, but the capsule presented different from others. And the leaf area, blade area and comparison of blade length to blade width of Jacaranda mimosifolia presented the same trend, as well as the capsule. And the limb circumference got a similar changing trend to the perforation number. Therefore, effects of varied nitrogen exponential fertilization treatments on seedling growth of Grevillea robusta and Jacaranda mimosifolia plants had highly consistency.