Phytolacca acinosa Roxb. and Oryza sativa L. were cultured in modified Hoagland medium containing 50, 200 and 800 µmol/L K+ respectively to analyze the morphological and physiological characteristics of Phytolacca acinosa. The results were as follows: The photosynthetic rate, transpiration rate, plant height and the root to shoot ratio exhibited no significant difference between the two plants, and Phytolacca acinosa grew normally in medium with different K+ concentrations. The Km was lower but the Imax was higher in the Phytolacca acinosa than those in the rice under K+ concentrations of 50 and 200 µmol/L . These results indicated that Phytolacca acinosa was more tolerable to low K+ stress and had higher potassium affinity than Oryza sativa.