A hydroponic experiment supplied with either sufficient P or deficient P was conducted to study the root morpholo- gy，root P uptake kinetic parameters and root secreted acid phosphatase activity of B56（P-efficient rice genotype） and B10（P-inefficient rape genotype）.Results showed that B56 showed greater P uptake than B10 at different P levels.Com- pared with B10，B56 had greater root dry weight，root length，root surface area and more lateral roots.B56 showed lower Km than B10 at dificient P treatment，whereas there was no significant difference in Imax or Km between B10 and B56 at sufficient P treatment.Low P treatment significantly increased the Imax，but significantly decreased the Km for both rape genotypes.B56 showed higher root secreted acid phosphatase activity than B10 at different P treatment;whereas there was no difference at sufficient P treatment.