<p>The development of magnesium (Mg) alloys characterized by exceptional mechanical properties and degradation performance for fracturing materials remains a challenge. Here, the overall properties of a Mg–Y–Zn alloy are greatly improved through replacing Zn with Cu and performing hot extrusion. The extruded Mg₉₅Y₃Zn₂, Mg₉₅Y₃Zn₁Cu₁ and Mg₉₅Y₃Cu₂ alloys (at%) consist of broken elongated LPSO phase, Mg matrix, and a small amount of particles. In comparison to the extruded Mg₉₅Y₃Zn₂ alloy, the extruded Mg₉₅Y₃Cu₂ alloy demonstrates comparable mechanical properties while demonstrating significantly enhanced degradation performance. Additionally, the degradation rate of the Mg₉₅Y₃Zn₁Cu₁ and Mg₉₅Y₃Cu₂ alloys immersed along longitudinal section is usually higher than that immersed along the transverse section. The synergistic effects of many factors (LPSO phase, grain size, dislocation density and corrosion product layer) result in elevated corrosion rates of the extruded Mg₉₅Y₃Cu₂ alloy. The composition and spatial distribution of the LPSO structure cause anisotropic corrosion occurring in Cu containing Mg alloys. The current findings offer significant theoretical insights for optimizing the composition of high-strength and rapidly degradable Mg alloy.</p> Graphical Abstract <p></p>