We describe a miniature diorama AR system called ‘Miniature AR’ which can be applied to a mechanical diorama to extend the content’s feasibility by overlapping virtual objects on the complex diorama structure. The previous AR researches for the diorama are usually based on 2D planar recognition, and multiple user experience cannot be considered due to multi-devices synchronization. To overcome these constraints, in this paper, we show a new diorama AR system suitable for a tiny complex structure. The contributions of our work are i) design of the diorama AR system, ii) AR space generation and 6DOF view device tracking for diorama, iii) multiple view and event synchronization for multiple users. The utility of the approach has been demonstrated under a real diorama environment (miniature of a ski slope) using mobile devices.