A new modified organo-bentonite using dithizone(D-O-bentonite) was used for preconcentration, separation and determination of silver(I) in natural water by flame atomic absorption spectrometry (FAAS). The experimental conditions for effective adsorption and elution of trace levels of silver (I) were optimized with respect to different experimental parameters. The influences of some common coexisting ions were also examined. The results show that the silver ion could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 4-8, the contact time was 15 min, and capacity of the sorbent was 19.7 mg·g-1. The silver(I) adsorbed on the sorbent could be completely eluated by using 1 mol·L-1 HNO3. The preconcentration factor is 100. The detection limit of the method for silver was 0.02 µg·L-1. The method was applied to the pre-concentration/separation of silver in the environmental water with satisfactory results.