The invention discloses a posterior cranium spreading drainage device for the neurosurgery department. The posterior cranium spreading drainage device comprises two L-shaped base plates which are oppositely arranged, skid-resistance grooves are formed in the outer side faces of the base plates, spreading plates are fixed to the left ends of the base plates, and square shafts are arranged in shaftholes of the base plates. The posterior cranium spreading drainage device for the neurosurgery department is simple in structure, through supporting of compression springs on the spreading plates, theposterior cranium tissue is spread, a flow guide tube is arranged between the two spreading plates for assembly and cooperation use, and the occupation of the space is reduced, so that the surgery view is wider; meanwhile, the device is conveniently operated by a single person, positioning sheets can achieve the effect of positioning, thus sliding and shedding of the spreading plates during spreading are prevented, and the overall stability is improved; through negative pressure generated during stretching of a gasbag, tissue hydrops is subjected to drainage, the negative pressure is uniformand stable, drainage is thorough, quick recovery of the illness state in the later period is facilitated, and the effect is good; meanwhile, the operation difficulty and burden of medical personnel are lowered, and the device is convenient to use.