Abstract: The physiological tolerance adaptation characteristics and the changes of berberine content in leaves of Phellodendron amurense seedlings were investigated under the simulated condition of drought using three different concentrations of polyethylene glycol (PEG 8000). The results showed that the contents of MDA in P. amurense seedlings under 5%, 10% and 20% PEG were different. Under the 5% PEG stress, MDA content reduced, and in the entire stress process were lower than that before treatment (P0.05). Under the 10% PEG stress, MDA content increased a little and a significantly increase appeared at the 9th hour (P0.05). MDA content showed a single peak curve under the 20% PEG stress. Membrane electrolyte leakage in leaves showed a fluctuated upward trend with the stress time, and the higher concentration of PEG damaged membrane more seriously. The content of proline decreased firstly, and then increased. Under higher concentrations of PEG, the proline content varied greatly. The activity of SOD increased firstly, and then decreased. With the increase of PEG concentration, the SOD activity peaks came earlier. Berberine content in the leaves increased at the beginning, and then decreased gradually with the increase of duration. Under higher concentration of PEG, the berberine content reached its peak earlier, while under lower concentration of PEG, the berberin content peak came later but the maximum value was higher.