Metal core bar can enhance the air permeability and improve the core strength. However

the traditional design method of metal core bar is very simple and mainly relies on artificial experience which makes the metal core bar material distribution unreasonable. Therefore

a topology optimization method for metal core bar structure was proposed in the sand casting. SIMP（Solid Isotropic Material with Penalizatio） topology optimization model was used to optimize the structure of metal core bar. Meanwhile

the optimized metal core bar was applied to the bending strength experiment of sand core. The experimental results reveal that difference between the bending strength before and after optimization can be neglected. Compared with the normal shape of the metal core bar

the weight of the optimized core bar is reduced by more than 59.9%

exhibiting a satisfied effects.