In this work, perfect elastic wave mode transmission and isolation in an anisotropic Pentamode Material (PM) slab sandwiched between two semi-infinite isotropic solids are first explored. Selective elastic wave mode filtering is achieved in a broad frequency range. Furthermore, elastic wave experiments are conducted, which are in good agreements with the full-wave finite element simulations. As a result, the anisotropic PM greatly expands the horizon of subwavelength elastic wave control with broadband advantage. Such filtering abilities can be very useful for underwater noise isolation and elastic wave manipulation devices.