In order to investigate the anti-seepage characteristics of Sidraton particles under different cover conditions, three earth rock-fill dam models with different hidden trouble of leakage were constructed. Sidradon particles with different blanket thickness and different blanket area were covered in the seepage area of dam surface and the change of seepage flow with time was recorded. The experiment shows that after covering the Sidraton particles, the seepage flow of the three leakage models decreases exponentially with time. The seepage flow of the contact leakage model decreases the most, and the seepage flow of the reservoir bottom leakage model decreases slowly. With the increase of blanket thickness, the anti-seepage effect of the three leakage models is enhanced. For the contact leakage model and the concentrated leakage model, the anti-seepage effect decreases with the increase of the blanket area. Hydrated Sidraton particles with a good anti-seepage ability can be used to prevent and repair the leakage of dam.