Connecting beam (CB) mandala is a kind of planar deployable mechanism with the ability of scaling up and down like a mandala flower. It is constructed by many-component connecting beams, which are identical circle arcs with specific arc angle and three revolving joints (one middle joint and two end joints) located symmetrically. In this paper, a detailed geometrical analysis of CB mandala is reported. Some basic concepts and parameters are proposed to describe CB mandala's geometry. Based on them, the scaling motion of CB mandala is analyzed, and its five morphologies and their unique features are presented. CB mandala's application is also discussed and illustrated with a simple case.