This paper bases on a seeking experiment of soil nails of cavern.It summarizes the key elements of the field test on dynamic resisting force of the loess cavern and gives the test results of the soil nails on top of the arch.According to the phenomena of the experiment,it contrasts the naked cavern,the soil nail support cavern on the relationship of the transient stress and the TNT quantity.It contrasts them on the relationship of the transient stress and the loading order,too.The naked cavern has the better ability of dying down the strain.The one-dimension viscoelastic Maxwell model is used in data fitting.In addition,it uses the same model to find the dynamic viscoelastic factor of building steel bar.The factor is approach to the naked cavern ones.