The invention provides a mythimna separata feeding device and method, and belongs to the technical field of insect feeding. The mythimna separata feeding device comprises a feeding box, a box cover, aexcrement recycling tray, an isolation net, a feed containing piece, an excrement filter screen, a pupa recycling box, an egg laying cage, a moisture preserving box, a moisture preserving piece, a feeding piece and an egg laying piece. Under a first state, the box cover is arranged on the upper surface of the feeding box, the isolation net is detachably connected to the bottom of the feeding box,the excrement recycling tray is detachably connected to the lower portion of the isolation net, and the feed containing piece is arranged in the feeding box; under a second state, the excrement filter screen is detachably connected to the bottom of the feeding box; under a third state, the pupa recycling box is arranged below the feeding box; under a fourth state, the egg laying cage is arrangedat the top of the feeding box, and the moisture preserving box covers the egg laying cage; and under a fifth state, the feeding piece and the egg laying piece are additionally arranged, and the moisture preserving piece covers the feeding piece and the egg laying piece. According to the device, mythimna separata with the age of more than 1 year is taken as a feeding whole body through cooperationof the assemblies, so that the manpower, space and feeding cost are greatly saved, and the feeding effect is good.