Abstract: Pot sand culture was set up for two inbred line maize with different phosphorus (P) efficiencies to investigate root physiological characteristics at seedling stage under P stress. When subject to low-P treatment, roots of low-P efficiency line 04065 have a significantly higher acid phosphatase (APase) activity during 4～8 leaf-stage and a lower P content than those of high-P efficiency line 04419. This indicates that root APase activity can be a suitable criterion for evaluating P efficiency of different maize inbred lines. With prolonged exposure to low-P stress (up to 6～8 leaf-stage), other physiological characteristics of maize roots, including root APase, root activity, MDA content, total root length and dry matter accumulation,except for root/shoot ratio, are significantly different between the two inbred lines. As such, tolerance of different maize genotypes to low-P stress is related to multiple physiological processes.