Abstract: In the process of sand mixing,the effect of the effective bentonite content of recycled sand on the performance of molding sand was studied with the change of sand mixing time. At the same time,with the change of bentonite supplemental amount,the influence of supplemental amount on the properties of molding sand was studied. The results show that the properties of molding sand vary with the content of available bentonite in recycled sand and the amount of bentonite added during sand mixing. The study result provides a guiding basis for determining and selecting the effective bentonite content of recycled sand and the addition amount of bentonite in sand mixing.