The utility model relates to a device for improving safety coefficient of a spiral case door of a hydropower station. The device comprises a spiral case man door base, wherein a spiral case man door is mounted on the outer side of the spiral case man door base through a plurality of occluding bolts, and a plurality of anti-unlocking fixing devices are mounted on the spiral case man door base. The utility model provides the device for improving the safety coefficient of the spiral case door of the hydropower station, by adopting the structure, potential safety hazard caused by a flooding accident of a factory building due to fracture of the occluding bolts of the outward opening type spiral case door of the hydropower station is eliminated, and the shortcomings of easiness in deformation of a door body, inconvenience in operation, larger size, more complex manufacturing and mounting, difficulty in field construction and the like of an improvement method of an inward opening type structure are overcome. The device disclosed by the utility model has the advantages of simple, economical and firm transformation construction and very high safety. Under the circumstance that the occluding bolts of the spiral case door are fractured, the flooding accident of the factory building can be prevented, a unit has time for shutdown and overhaul, and the potential safety hazard caused by flooding of the factory building due to the fracture of the occluding bolts of the spiral case door can be fundamentally avoided.