The invention discloses a method for breeding aphidius gifuensis ashmead through floating tobacco seedlings, particularly relates to a method for breeding aphidius gifuensis ashmead through floating tobacco seedlings, which is realized through breeding aphids by cultivating uniform, robust tobacco seedling with proper density and inoculating mummified aphids under net covering condition, and belongs to the technical field of insect breeding and biological control of injurious insects. According to the technical system for breeding aphidius gifuensis ashmead efficiently through floating tobacco seedlings, innovation is achieved in the three aphidius gifuensis ashmead breeding steps including host plant cultivation, host myzus persicae breeding and aphidius gifuensis ashmead breeding, the aphidius gifuensis ashmead breeding cycle is shortened to be two months, and the number of mummified aphids and parasitic aphids existing in each square meter can reach over one hundred and twenty thousand; the steps such as tobacco plant transplantation and cultivation are omitted, management is easy and convenient, and a small number of manpower and material resources are needed. By the adoption of the method for breeding aphidius gifuensis ashmead through floating tobacco seedlings, the aphidius gifuensis ashmead can be bred by fully utilizing existing breeding facilities, aphidius gifuensis ashmead breeding facility investment is reduced, and aphidius gifuensis ashmead breeding cost is reduced. The method is tested in large-scale aphidius gifuensis ashmead breeding work, the time efficiency, the unit-area efficiency, the management efficiency, the aphidius gifuensis ashmead breeding facility utilization rate and other aspects of large-scale aphidius gifuensis ashmead breeding are improved comprehensively, the aphidius gifuensis ashmead breeding cost is reduced greatly, and the method for breeding aphidius gifuensis ashmead is adopted by most tobacco enterprises in China.