Additives of a polyamic acid resin composition are disclosed, including an ester-phenol compound, an imidazole compound, and a heterocyclic aromatic amine compound other than the imidazole compound. The high cyclization temperature and long cyclization period of conventional polyamic acid resin compositions can be lowered and shorten by the additives of the invention. In addition, a metal foil and the polyimide resin formed from the cyclization have excellent adhesive strength, high flat degree, and excellent electrical property.