The strength of lightweight aggregate concrete depends basically on the mortar strength and the packing strength of lightweight coarse aggregate. The former can be adequately estimated based on the water/cement ratio, but there has been no appropriate method to determine the latter. In this study, a series of experiments were carried out to explore a method to evaluate the packing strength of lightweight coarse aggregate. Test results have shown that for lightweight aggregate concrete a dividing strength indeed exists. In addition, the dividing strength can then be reasonably adopted as an indicator in representing the packing strength of lightweight aggregate. Finally, as the maximum size or the volume content of the coarse aggregate varies, the corresponding packing structure and the packing density of the lightweight concrete will be different, leading to a change of the dividing strength.