The invention discloses a mixed culture method for lotus roots and red carps. The method comprises the steps of basal dressing, lotus root planting, red carp putting, bait feeding and topdressing. According to the mixed culture method, the growing environment needed by the lotus roots and the red carps is fully utilized, the red carps like digging mud and looking for food, therefore, the carps can help form viscous mud with appropriate tightness to adapt to growing of the lotus roots; meanwhile, the lotus roots need to breathe air to grow, the air is transmitted through holes in the lotus roots, and therefore the requirements are met while enough oxygen content is supplemented to the carp group; culturing of the carp group and growing of the lotus roots supplement each other, acidic fertilizer rich in organic matter is applied in the mud, therefore, the rhizomes of the lotus roots are fat and fleshy, the lotus root flesh is thick and solid, the lotus root shape is thick, and the quality is high.