Based on the original paper pouch system, the author changed the method of phosphorus (P) supply, and studied the regulation of soybean root architecture by P spatial availability and its genotypic variations on specially designed paper pouch system. The results showed that: 1) Improved stratified-P treatment could represent the distribution of P in the agricultural soil, and more efficiently regulated root architecture changed. Stratified-P treatment, namely upper part was in high P conditions and lower part was in low P conditions, led to longer total root length, more root surface areas and increased the distribution of roots in upper high P part, root system became sallow, finally increased plant P uptake and biomass. 2) For the regulation of root architecture by stratified-P treatment, there was a significant genotypic difference between soybean genotypes with different P efficiency. P-efficient genotype, HN89，could respond to P spatial availability faster than P-inefficient genotype, HN112, and changed considerably on root architecture parameters, finally had higher P uptake and biomass.