The invention provides a method for preventing and treating soft shell disease of penaeus vannamei, and belongs to technical field of biological disease prevention. In the breeding process, the penaeus vannamei is molted in molting stages or due to outside stress and can be supplied with a soft calcium supplement, wherein the soft calcium supplement comprises nutrition calcium A and nutrition calcium B, the nutrition calcium A contains one sixth sodium percarbonate and five sixths amino calcium gluconate; the nutrition calcium B is food-grade calcium lactate of more than 90%; and the splashing concentration of the nutrition calcium A in the soft calcium supplement is 1.5ppm-3ppm, and the splashing concentration of the nutrition calcium B is 0.2-0.3ppm. The method has the beneficial effects of preventing and treating incapability of hardening the body shells, commonly known as soft shell, of the penaeus vannamei after being molted in molting stages or due to outside stress in breeding process, having obvious effects on hardening the shells, building a body and strengthening the body, and eliminating the sub-health condition of the penaeus vannamei.