The photocatalysis of nanometer TiO2/Ag was modi- fied by sodium dodecyl sulfate,and its behavior of adsorption for pesticide was investigated on the surface of catalyst.Four kinds of water-olubility preparations were prepared by using TiO2/Ag,modified TiO2/Ag by 0.5% SDS,TiO2 and nothingness as photocatalyst with dimethomorph as effective compo- nent.They were besmeared on a piece of glass,and the photocatalytic experiment was done in sunlight.Degradation rates of 1.2% di- methomorph are 71.5%,68.0%,45.5% and 28.3%,respectively,when it was degraded in five days.Degradation rate of 10% dimetho- morph is 97.3% in eight days in sunlight and t1/2 is 2.8 d in nano-preparation,when it was sprayed on small cabbages after being diluted in rudimental experiments of toxicity for crop.The nano-preparation is of better biologic activity,the virulence of which is 1.235 times as great as original pesticide and 1.245 times as ordinary preparation under the same con- dition. The photocatalysis of nanometer TiO2 / Ag was modi-fied by sodium dodecyl sulfate, and its behavior of adsorption for pesticide was investigated on the surface of catalyst. Flexible kinds of water-olubility preparations were prepared by using TiO2 / Ag, modified TiO2 / Ag by 0.5% SDS, TiO2 and nothingness as photocatalyst with dimethomorph as effective compo- nent. They were besmeared on a piece of glass, and the photocatalytic experiment was done in sunlight. The degradation rates of 1.2% di- methomorph are 71.5%, 68.0% , 45.5% and 28.3%, respectively, when it was degraded in five days. The degradation rate of 10% dimetho-morph was 97.3% in eight days in sunlight and t1 / 2 was 2.8 days in nano-preparation, when it was sprayed on small cabbages after being diluted in rudimental experiments of toxicity for crop. The nano-preparation is of better biologic activity, the virulence of which is 1.235 times as great as original pesticide and 1.245 times as ordinary preparation under the same con- dition.