Abstract: Many aquatic plants play an important role in the immobilization of nitrogen and phosphorus in the wetland soil. Gray correlation analysis was conducted in this study to clarify the relationship of nitrogen and phosphorus contents between the organs of Phragmites australis(common reed)and soil in different depth in Qinhu Lake wetland. The results show that: ①The distribution pattern of nitrogen and phosphorus in the organs of common reed were the same: the total nitrogen contents were with the order of leaf >spike>root > stem and the total phosphorus contents were with the order of leaf > root >spike> stem. ②The interaction of nitrogen and phosphorus between common reed and soil mainly concentrated in the 0-30 cm soil layer due to the vertical distribution of reed roots. It indicated that the fixation of nitrogen and phosphorus in the soil-vegetation system concentrated in the surface of soil. ③In the growth period(spring and summer), the interaction of nitrogen and phosphorus in soil-vegetation system primarily occurred in the soil surface. At the same time, a close association of nitrogen and phosphorus contents between ≥45-60 cm depth of soil and the common reed was observed in this study which may be caused by the rising of underground water level.