The impact of Y content on the microstructure, mechanical properties, and electromagnetic interference shielding effectiveness (EMI SE) of the Mg−6Zn−xY−1La−0.5Zr alloy was investigated. After the extrusion treatment of Mg−6Zn−xY−1La−0.5Zr alloy, the large grains that did not experience dynamic recrystallization were elongated along the extrusion direction, and the small-sized dynamic recrystallized grains were distributed around the large grains. The Mg−6Zn−1Y−1La−0.5Zr alloy demonstrated a favorable balance between strength and plasticity, exhibiting ultimate tensile strength, yield strength, and elongation values of 332.3 MPa, 267.3 MPa, and 16.2%, respectively. Moreover, the EMI SE within the frequency range of 30−1500 MHz changes from 79 to 110 dB, aligning with the electromagnetic shielding requirements of many high-strength applications.