The invention discloses an improving method for a core wall dam aseismic structure and adopted reinforced chain nets. The improving method for the core wall dam aseismic structure is the improvement on an existing earth and rockfill dam top aseismic reinforcement technical scheme. According to the specific method, the reinforced chain nets are adopted for replacing existing hard steel bar nets to adapt to the deformation character in the enrockment granular soil construction period; the reinforced chain nets are horizontally laid within the height H range of the reinforcement area of the dam top in a layering manner; and the reinforced chain nets are located on the two sides of an anti-seepage core wall located in the dam correspondingly. According to the improving method, the problems that reinforcement materials are poor in durability, prone to damage or uncoordinated in deformation or the like are solved, the reinforced joint connecting manner is further optimized, and field construction is convenient.