Abstract: The size and mechanical properties stability of the high-strength aluminum alloy cylinders was studied after long term loading under condition of constant temperature and constant load. The results show that after loading of 0.78σ0-0.92σ0 for about 2×104 h at 40 ℃, the roundness of the high-strength aluminum cylinders decreased on different degree, the creep rate of the cylinders submitted exponential relation with the load, and the loop mechanical properties of the cylinders were stable.