Storytelling is one of the effective methods used in education. Computer-aided storytelling allows children to create more free-form stories and provides a large amount of story materials. Grounded in the current related works, we propose and design a tangible interactive tool, which supports children to interact with virtual objects via a tangible way instead of the usage of mouse/keyboard. With this tool, we also develop a system called StoryCube where children are able to create a 3D story environment and accomplish story narrations through physical manipulations to different virtual characters. From a preliminary user study, we find StoryCube full of playfulness, easy to learn and use, and somehow inspire children in storytelling activities.