The (Zr_0.55Cu_0.3Al_0.1Ni_0.05)_100-xEr_x (x=0, 0.5, 1, 2, 3, 4, 5) Zr-based bulk alloy with diameter of 3 mm was prepared by water-cooled copper crucible smelting and copper mold suction casting using zirconium sponge as raw material. By comparing the microstructure and mechanical properties of sponge Zr-based alloy with different Er contents, the influence of Er on the amorphous forming ability, thermal stability, and mechanical properties of Zr-based bulk alloy was studied. Results show that when the zirconium sponge is used as the raw material, the amorphous formation ability and mechanical properties of sponge Zr-based alloy are obviously reduced. The sponge Zr-based amorphous alloy cannot be prepared when x=0. After adding Er element, the amorphous forming ability and mechanical properties of the sponge Zr-based alloy with the amorphous structure are improved obviously. The optimal mechanical properties of the sponge Zr-based alloy are achieved when x=2: the compression strength σ_bc is 2142.5 MPa and the plastic strain ε_p is 10.01% at room temperature. Compared with the amorphous (Zr_0.55Cu_0.3Al_0.1Ni_0.05)₉₈Er₂ alloy with the diameter of 3 mm prepared from high-purity Zr, the compressive strength and plasticity at room temperature of the sponge Zr-based alloy recovers by 97.63% and 69.95%, respectively. The Er addition is beneficial to improve the amorphous forming ability and mechanical properties of sponge Zr-based alloy, which also provides a new approach for low-cost preparation of Zr-based amorphous alloy.