The utility model discloses a clamping device for turning a guide vane of a gas turbine. An existing conventional pressing plate directly presses a shroud, pressing points are concentrated at two points, stress is concentrated, and the shroud is prone to deformation. The utility model discloses a clamping device for turning a guide vane of a gas turbine. The clamping device comprises a triangularpressing plate, a first stud, a second stud and a nut, the bottom edge of the triangular pressing plate is arc-shaped, an edge cutting groove is formed in the arc-shaped bottom edge, a through hole and a screw hole are formed in the plate face of the triangular pressing plate, the through hole is close to the bottom edge, and the screw hole is close to the vertex angle opposite to the bottom edge.The device can directly press the guide vane shroud, the pressing area is increased through the triangular pressing plate, stress is more uniform, the machining stability of the shroud is improved, and the surface quality of inner hole turning is improved.