The compressive creep curves of Mg-4Al-5.1Y-2.5LPC alloy in T6 condition were tested under different stresses and temperatures using an electronic creep testing machine. The results show that the stress exponent of Mg-4Al-5.1Y-2.5LPC alloy at 250? is 3.38, indicating the creep mechanism of Mg-4Al-5.1Y-2.5LPC alloy is dislocation climb. When the creep stress is 117.1MPa, the creep activation energy (Q 200-250?) of Mg-4Al-5.1Y-2.5LPC alloy is 145.7 kJ/mol, approximately being equal to self-diffusion activation energy of Mg, which also shows that the dislocation climb plays an important role in the creep process of Mg-4Al-5.1Y- 2.5LPC alloy.