Abstract: This article mainly discussed the effect of phosphorous levels on the glutamine synthetase (GS) activities in soybean functional leaves at different growth stages and soybean seeds. Three soybean genotypes were used, including Dongnong 42 (high protein cultivar), Hefeng 25 (middle cultivar) and Dongnong 46 (high oil cultivar). The soybean seeds were planted in pots and fertilized with 0.033 g of N and K2O per kg soil. Four levels of phosphorous treatments were designed, which were P0, P5, P10 and P15 (i.e., 0, 0.033, 0.067 and 0.100 g of P2O5 per kg soil). The results showed that the highest GS activity in functional leaves and seeds of Dongnong 42 and Hefeng 25 appeared under P10 treatment; while in Dongnong 46, the highest GS activity in functional leaves was determined under P10 treatment and that of seeds was detected under P5 treatment. In the same treatment among cultivars, the highest GS activity in functional leaves and seeds was in Dongnong 42, the lowest one was in Dongnong 46 and Hefeng 25 was in the middle of the three cultivars. In each cultivar under each treatment, the highest value of GS activities in functional leaves was all determined at pod setting stage. The highest values of GS activities in seeds could be maintained much longer in Dongnong 42, but could be maintained shorter in Dongnong 46. The phosphorous treatment has an effect on the GS activities of leaves and seeds，and an appropriate phosphorous treatment is beneficial to improving GS activities.