Abstract: A parameterized practical calculation method is proposed to investigate the lateral stability of a parabolic double-rib arch under non-directional loads. The effects of structural parameters on the lateral stability are analyzed. The research shows that due to the action of non-directional loads, the critical lateral stability load increases remarkably for a through-arch and decreases evidently for an upper loading arch, and that the stiffness of lateral bracing, the ratio of rise to span and the lateral rigidity of a deck system have a great effect on the critical load.