Abstract: The unfolding mechanical behaviours of coilable space mast are deeply influenced by the properties in coiling process. Whether the coiling process can be conducted successfully or not depends on the stiffness ratio of the longeron and triangular batten, which is most important in engineering design. The non-hinge continuous longeron and triangular batten experience large rotation and deformation in the coiling process, while the battens exhibit snap-through behavior. In the paper, the post-buckling analysis of triangular battens was carried out by the principle of potential energy and geometry exact theory. The equilibrium equation was also derived by the principle of potential energy. To verify the theoretical derivation and make accurate predictions of coiling process, the adaptive arc-length iteration method and nonlinear finite element method were employed for the post-buckling numerical simulation. The snap-through problem, stress, strain, and energy status in coiling process can be predicted comprehensively. A few comparisons between numerical and analytical results, such as the equilibrium equation, the applied torque, the tip point height, the minimum stiffness of the triangle batten, and the energy are carried out to verify the reliability of the analysis and calculations. The proposed formulas mutually supply the exact simulations by incremental finite element method and will contribute to the design process of coilable masts.