A dual structural bone ash casket is composed of an inner container and an outer container. The inner container is made of fire-proof material for preserving bone ashes. The top edge thereof is provided with several tapped holes, and along the edge of its lid is also provided with corresponding screw passing holes so as to tighten the lid on the inner container with a fixing screw. The outer container enclosing the inner one, is made of a hardened liquid plastic material with its surface ornamented by striae of imitated marble, porcelain, or wood. The outer container also has a lid to cover it. With such a dual structure formed of different material, the bone ashes can be securely and eternally preserved.