Abstract: Effects of different acid-aluminum treatments on the four Fast-growing Eucalyptus clones (Eucalyptus grandis E. urophylla Guanglina No.9, E. grandis E. urophylla No.12, E. urophylla No.4, E. urophylla E. camaldulensis No.3) were studied using the cultivation method of sand and soil combination. The acid and Al levels were pH 3.0＋0 mg/L Al3+, pH 3.0＋120 mg/L Al3+, pH 4.0＋0 mg/L Al3+, pH 4.0＋120 mg/L Al3+ for each clone, and the pH 4.8＋0 mg/L Al3+ was used as the corresponding control, respectively. The results show that the morphology, growth, water content, cholorophyll content, proline content and membrane permeability in four Fast-growing Eucalyptus clones are affected under the different acid-Al treatments. All clones are significantly inhibited under the pH 3.0+120 mg/L Al3+ treatment, the leaves and buds are distorted, the seedling heights and collar diameters are depressed, the membrane permeability is degraded, and cholorophyll content and water content are decreased. While the proline contents of the clones are accumulated. The four clones respond to the acid-aluninum differently. E. grandis E. urophylla No.9 has the best adaptation to the acid-aluminum treatments from the growth and physiological indexes, such as non-significant morphology change, low amplitude variation of membrane permeability, cholorophyll content and water content, and high amplitude variation of proline content. E. urophylla No.4 has the weakest intolerance with great damage, even faded leaves and buds. The resistance intensity is in order of No.9 No.12 No.4 No.3. Choosing and culturing Eucalyptus clones with resistance to acid-aluminum should be considered one factor to improve the site productivity on the acid soil with enriched aluminum in the south area of China.