A polysilicon defect improving method comprises the following procedures that: a silicon dioxide layer is formed on a silicon substrate; a polysilicon attaching plug is formed on the silicon dioxide layer and runs through the silicon dioxide layer; a silicon nitride layer is formed on the silicon dioxide layer and is covered with the polysilicon attaching plug; an interlevel medium layer is formed on the silicon nitride layer; the interlevel medium layer on the upper part of the polysilicon attaching plug is etched to form an opening; the silicon nitride layer in the opening is etched to expose the polysilicon attaching plug; the opening is filled with polysilicon and is communicated with the polysilicon attaching plug. Through the procedures, the reaction between thermal standard cleaning liquid No 1 and the polysilicon attaching plug can not be produced because of the protection of the silicon nitride layer; as the silicon nitride layer is etched finally, therefore, the silicon nitride layer is not exposed to make the subsequent filling flat.