The invention discloses a neurosurgery department back cranial opening drainage device. The neurosurgery department back cranial opening drainage device includes a base; the base is a [-shaped plate;fixing plates are fixedly on upper surfaces of two ends of the base and opposite to each other; rotation shafts are arranged in shaft holes formed in the fixing plates; the neurosurgery department back cranial opening drainage device has a simple structure, can be fixedly through the base, can open a skull at an operation position through opposite motion of two pulling plates, can lead intracranial leaked blood to a negative pressure barrel through a drainage catheter and a negative pressure pump; a high position of a liquid outlet of the drainage catheter can effectively prevent liquid in thenegative pressure barrel from flowing down; an angle of deflection of an arm plate can be adjusted, and a position of a sliding seat on the arm plate can be adjusted; the heights of the pulling plates and the drainage catheter can be correspondingly adjusted, the drainage catheter can safely enter a cranium and reaches a designated depth position, the successful rate of the operation can be improved, the risk of complications can be lowered, and the working difficulty of medical workers can be lowered.