In the runoff and soil erosion field experiment plots，the impacts of different dosages of water retention agent application on contents and availability of trace elements in purple soils were investigated. Five different dosages of water retention agent included 0 kg/hm²(T0)，30 kg/hm²(T1)，90 kg/hm²(T2)，150 kg/hm²(T3)and 210 kg/hm²(T4).The results showed that the order of the soil total trace elements were Mn(134.68±11.02)mg/kg>Zn(69.46±5.24)mg/kg>Fe(24.02±3.03)mg/kg>Cu(17.42±12.17)mg/kg>Mo(1.04±0.17)mg/kg and the availability of trace elements showed the similar change trends. The total and availability of Mn were increased as the dosages of water retaining agent were increased(T0Cu>Mn>Fe>Zn. This study could provide the theoretical basis and data supports for the enhanced anti-drought ability，reasonable supply of trace element fertilizers and the reasonable evaluated the soil fertilization condition.