Abstract: Crack propagation rate tests of 7055-T76511 aluminum alloy section material under different temperatures (150 ℃, room temperature, -70 ℃)and stress ratios (0.1, 0.5) were carried out. The effect of temperature and stress ratio on crack propagation rate and threshold of the alloy was studied. The results show that with decreasing temperature and stress ratio, the threshold for crack propagation of 7055-T76511 aluminum alloy gradually increased, and the crack propagation rate gradually decreased. At -70 ℃, the crack growth rate when the alloy fractured was smaller, and the crack growth threshold was larger, showing the best crack growth resistance.