Abstract: Four soybean genotypes with different phosphorus(P) efficiency were studied in main root length, root/shoot ratio, photosynthetic rate, chlorophyll content and the ability of resistance to senility in solution culture under P deficiency stress. Results showed that P deficiency stress stimulated root growth. Compairing with P-inefficent genotypes, main root length and root/shoot ratio of P-efficent genotypes increased significantly under P deficiency stress, and photosynthetic rate and ability of resistance membrane lipid peroxidation of P-efficent genotypes were higher than that of P-inefficent genotypes.