Omnidirectional stereovision is beneficial in wide applications due to its large field of view. Traditional implementation of such a system employs two separate cameras looking at separate mirrors to achieve 3D stereo reconstruction. In this paper, a compact omnidirectional multi-stereo system that consists of only one camera and multiple mirrors is proposed. The novelty lies in the designing of a principal mirror above the array of sub-mirrors to achieve multiple omnidirectional stereo pairs that have appropriate baselines and multiple viewpoints in a compact manner. The system's imaging projection and error propagation model are presented. Experiments based on simulation and real data verify the effectiveness of our system.