Abstract: The differences in phosphorus efficiency among 8 hydrid poplar clones of S17, (Populus deltoides×P. cathayana), S19, (Populus deltoides×P. cathayana), 105 (Populus deltoides×P. simonii), 106(Populus deitoides×P. simonii ), I- 69 (Populus deltoides Bartr. cv. Lux), 797 (Populus deltoides×P. euramericana ), 1388 (Populus deltoides×P. euramericana), and 3244 (Populus deltoides ) were studied by the method of soil culture in greenhouse. The results showed that the phosphorus efficiencies varied among the treated poplar clones, as indicated with the above- ground biomass of clones under P deficient stress. Clone S17,S19,and 105 were efficient phosphorus absorbers and ranked in Grade A of high phosphorus efficiency because of their large biomasses of 55. 15, 48. 28 and 49. 25 g/seedling, respectively; and comparative small biomass decrements (less than 30% ). Similarly, the phosphorus efficiencies of clone 106, 797, and I- 69 were considered as Grade C, as associated with their quite lower biomasses of 35. 45,31. 45 and 28. 35 g/seedling, respectively; and their larger biomass decrements(around 50% ) in - P treatments, in comparison with +P treatments. The biomass of 1388 and 3244 were the lowest, only 23. 05 and 23. 94 g/seedling, therefore, the most inefficient P absorbers of Grade D. None of the poplar clones was found as Grade B in this study.