Abstract: This paper is concerned with the out-of-plane stability and design of close-section arches under compression and bending. Firstly, the out-of-plane elastic buckling loads of arches under uniformly-distributed compression and bending are studied by a potential energy principle. After that, the moment of cross-section is considered as the decrease effect on the out-of-plane inelastic stability of arches, and a normalized slenderness considered the decrease effect is proposed. Based on the results proposed, the out-of-plane inelastic design of arches under compression and bending is simplified into inelastic design of compressed arches. The out-of-plane design method agrees well with finite element results. Thusly, it could be used to design the out-of-plane inelastic stability of steel arches.