A kind of high-damping mortar layer applied to damped infill wall was designed, and the pseudo-static experiments were carried out, also its mechanical properties were studied. The results reveal that: compared with common mortar layer, high-damping mortar layer has greater energy dissipation and horizontal shear deformation capacity in damped infill walls. When the polymer-cement ratio is in the range of 0.38~0.53, with the increase of polymer content in high-damping mortar layer, the energy dissipation and horizontal shear deformation capacity of mortar layer in damped infill walls will be enhanced; the optimal polymer-cement ratio is 0.45. With the increase of the thickness of high-damping mortar layer, horizontal shear deformation capacity of mortar layer in damped infill walls will be improved, the slip between the upper masonry and high-damping mortar layer will be delayed, this enhancing its energy dissipation capacity; however, with the increase of the thickness of high-damping mortar layer, the ultimate bearing capacity of mortar layer in damped infill walls will be reduced, the better value of thickness of high-damping mortar layer is about 9 mm.