Abstract: The researches on vertical strip slab pullout issue have problems of artificial distinguishing of shallow and deep buried types, non-uniform understanding of definition standard and symmetry of mechanical model. Based on the self-developed visual horizontal drawing strip anchor model tests and numerical simulation tests, the displacement and deformation laws of soils before plate in the drawing process are studied. Under the ultimate drawing, a triangular elasts core exists before the plate, and its angle’s variation can reflect the symmetry of slip-line field. When the buried ratio increases, the upper angle of the core increases along with the upper slip-line shrinking from surface to the plate, and the lower angle decreases, along with the lower slip-line relatively extending. The sum of two angles basically remains unchanged, but the slip-line field before the plate gradually evolves from asymmetric to symmetrical. On this basis, the corresponding assumptions are put forward to establish the ultimate bearing mechanical model for horizontally drawing vertical strip anchors, and the unified theoretical formula for the ultimate bearing capacity is derived, which can take the buried depth and other factors into consideration. The results indicate that the new model can reflect the continuous variation rules of the symmetry of the slip-line field with the depth ratio very well, and any further distinguishing of shallow and deep buried plates is not needed. The new unified ultimate bearing capacity's theoretical solution has good applicability to vertical strip anchors in sand, and the calculated results are in better agreement with the experiments, which shows an obvious advantage over the other three traditional methods.