A large-dip-angle self-leveling device is provided. The device comprises a mounting base platform arranged on a mounting stand column and a support cylinder connected with the mounting base platform. A leveling plate is arranged at the top of the mounting base platform, and a leveling platform is arranged on the leveling plate. A spirit bubble indicator and a control circuit board are arranged on the leveling platform. A connecting rod of balance weight is arranged in the support cylinder, one end of the connecting rod of balance weight is connected with the leveling platform, and the other end is connected with a balance weight. A four-core cable penetrates through the connecting rod of balance weight and the balance weight. Observation windows are symmetrically arranged at the lower part of the support cylinder. A melting pool is arranged at the bottom in the support cylinder.