Abstract: A ring triangle method was proposed to evaluate the dimensional stability. The dimensional stability of 7050 aluminum alloy was evaluated by the change of vertex angle and parallelism of two sides after opening of the ring triangle specimen along the bottom line. The cryogenic treatment and solution aging of 7050 aluminum alloy were combined to explore the influence of different processes on the dimensional stability of 7050 aluminum alloy ring triangle. The results show that the change of vertex angle and parallelism in quenched ring triangular specimen was the largest, while the change of vertex angle and parallelism which in specimen treated by conduction of cryogenic treatment after solution and prior to aging was the smallest. The results of dimensional stability was in good agreement with the result of residual stress, which show that the ring triangle specimen method can effectively evaluate the dimension stability from the residual stress layer.