Deployable coilable tape-spring booms have many advantages especially for use in space, such as light-weight, high folded-ratio and small storage volume. The boom’s folding and deploying process is accompanied with the large-scaled deformation of thin-walled materials, which may damage the boom on stress concentration points. For the sake of avoiding failures during coiling and deployment process, this paper aimed at acquiring the critical points on a boom which were vulnerable to be destroyed. Since the interactions of the boom’s infinitesimals were complicated, a numerical model was considered to be introduced. Meanwhile, the mechanical properties of the boom’s deployed state were also analyzed for a better design, and both the deploying and deployed behaviors were further analyzed through parametric study. The research of this paper will give more guidance on the design of tape-spring booms and the selection of the key parameters.