Abstract: Riparian zone with a certain width is commonly formed around many large reservoirs due to the seasonal change of water level. Adsorption and release behavior of phosphorus in soils of the zone would affect the surrounding water environment. In the present paper， Xinanjiang reservoir region was selected as the research area， the adsorption capacity and adsorption\|release behavior of phosphorus in soils of the riparian zone were studied using indoor simulation methods. The results showed that soils in the riparian zone had a medium phosphorus adsorption capacity. The maximum P sorption capacities ranged from 197.6 to 659.6 mg·kg-1 with a mean of 438.5 mg·kg-1. The equilibrium phosphorus concentration at zero phosphorus sorption of soil （EPC0） could be used as a threshold to evaluate release potential of soil phosphorus. Phosphorus was released from soils when EPC0 of the soils was greater than phosphorus concentration in the water. In contrast， soil could fix P from the water when EPC0 of the soils was less than phosphorus concentration in the water. EPC0 values of the tested soils ranged from 0.009 8 to 0.55 mg·L-1， with an average of 0.086 mg·L-1， which were linearly correlated with soil available P contents. When the initial phosphorus concentration in solution was set below 0.12 mg·L-1， the performance of most riparian soils belonged to the release\|retention alternation in interaction between soil and solution， except the individual soil with high P accumulation belonged to release pattern. Phosphorus release risk of soils would increase if riparian zone was temporarily used for agricultural production. In the present water quality situation of the reservoir region， when soil available P content exceeded 11 mg·kg-1， it would present phosphorus release behavior.

Key words: Xinanjiang reservoir, riparian zone, phosphorus, soil, water