The invention relates to a method for cascade disposal of arsenic-containing waste acid through copper slags, and belongs to the technical field of heavy metal arsenic pollution disposal and industrial solid waste comprehensive utilization. According to the method, the copper slags, the waste acid and an H2O2 solution are uniformly mixed, an arsenic precipitating reaction is carried out for 3-5 hours under a stirring condition of 70-90 DEG C to obtain a solid-liquid mixture A, and through solid-liquid separation, an arsenic-containing solid substance A and a filtrate A are obtained; the wasteacid is added into the filtrate A, air is continuously introduced under a stirring condition of 85 DEG C or above for 12-16 hours of an arsenic precipitating reaction to obtain a solid-liquid mixtureB, and solid-liquid separation is conducted to obtain an arsenic-containing solid substance B and a filtrate B; an alkaline substance is added into the filtrate B, the pH of the solution is adjusted to 7-8, and purification treatment is conducted to obtain industrial standard-reaching water. According to the method, the technological process is simple, the arsenic removal effect is significant, and the arsenic-containing solid substances are stable; the solid waste of a nonferrous metallurgy plant is comprehensively utilized for waste liquid disposal, and an efficient and low-cost method is provided for disposal of the heavy and nonferrous metallurgy smelting waste liquid.