Abstract: The YONGLE big bell and the wood-rack for suspending the big bell arevaluable antique relics. Their safety and reliability have attractedmuch attention of scientists and engineers. In the present paper apreliminary study on stability of the trapezoidal wood-rack is carried out.Based on a simplified bending constitutive model of the mortise andtenon joint(in Chinese it is called ``MAO-SUN'') between beams and pillars of the rack,the influence of the side-angle of the pillars on the stability of the rackis analyzed. The energy method of stability theory of elastic structures andthe comparison method are used. The formulas for the critical loadare derived for the reduced two dimensional trapezoidal rack structures. Thecritical loads are computed for the wood-rack with different side-angles, aswell as for that without side-angle. The results are compared witheach other for different racks with different side-angles. It isconcluded that the wood-rack with side-angle has better stability ascompared to that without side-angle. The wood rack design with inclinedpillars is a typical design of wooden architectures in ancient China andshows the wisdom of designers and craftsmen.