Abstract: A method for sample preparation of 129I in seawater by aircarrier separation is applied for AMS measurement in the present study. The seawater with carriers is added firstly for oxidationreduction reaction. The product I2 is collected by absorption apparatus, concentrated and purified by anionexchange resin afterit was blown-off under the condition of heating. The final sediment AgI will be used in AMS analysis. The method recovery rate obtained is from 50% to 70%. The advantage of this method is that the all procedures are proceeded in a closed system to prevent the loss of I2. It is much flexible compared to traditional extraction reverse extraction method and organic reagents are not necessary. The method in the present study can be widely used in solid, liquid and gas samples.