The invention discloses a protection device for a main computer which is moisture-proof and anti-collision, which comprises a casing, a main protection plate, a top plate, a secondary protection plate, a main limit plate, a secondary limit plate, a limit spring, a telescopic spring, a secondary protection groove, Drawers, connecting rods, pull rings, sliding rods, fixed rods, moving blocks, pull rods, arc-shaped plates, protective springs, rotating rods, connecting blocks, connecting springs and bumps. One end of the housing is provided with a secondary protective groove. The present invention squeezes the limit spring and the telescopic spring through the main protective plate and the secondary protective plate. The limit spring and the telescopic spring generate a reverse elastic force after compression, thereby pushing The main protective plate or the secondary protective plate moves away from the placement slot, so as to fix the host, dehumidify the air in the host through the desiccant, achieve the function of moisture-proof, protect the host, and save the time spent on the repair of the host. Improve work efficiency.