Abstract: Inflatable anchor is a new type of under-reamed anchor. The pullout tests on the inflatable anchor are carried out to analyze its deformation and bearing mechanism. According to the volume-pressure relationship of the anchor, the deformation characteristic of rubber membrane is studied when being inflated with water. And the inflated shape of rubber membrane in soft soil is approximately cylindrical, which is mensurated by injected cement slurry. On such a basis, a series of scaled pullout tests are performed with various inflatable volume. The results show that the ultimate loads and displacements of inflatable anchor both increase with the increment of the volume. As for the large tensility and small tensile strength of rubber membrane to bear loads, two methods which are improved by wire or grouting are designed, and the results of pullout tests are analyzed comparatively. The results show that the inflatable anchors with wire transfer the loads from rubber membrane to wire, which enhances the bearing capacity of the anchor greatly. And the inflatable anchor with grouting has a small displacement. It combines the advantages of inflatable anchor and grouting anchor. These two improved methods are useful to the practical application of inflatable anchors.