What material is best for filling cavities in children is related to the specific situation. When the cavity is formed in the milk molar, due to the short crown and poor retention, it is best to apply silver amalgam and other filling, which can avoid fracture when bearing large biting force, and can better restore the anatomical form and improve the chewing efficiency. When carious lesion is formed on the milk cusp teeth, it is better to apply glass ion cement filling, the fluorine ion contained can promote the enamel remineralization and avoid the expansion of carious lesion, and the glass ion cement is not easy to form the overhang and will not stimulate the gum redness and swelling. When the caries is formed in the milk front teeth, the composite resin with strong adhesion can be used to fill it, which can achieve the color close to the natural teeth and play a good aesthetic role.