To study the mechanism of structure damage and the law of performance weakening of TiAl alloy turbine under pressure, an experimental method is designed that compresses and then stretches the TiAl alloy turbine. The slips and microcracks on the surface and inside of the compressed turbine journal are analyzed by scanning electron microscope (SEM), and the tensile fracture morphology is observed. The experimental results show that the residual tensile strengths of the compressed TiAl turbines gradually decrease as the pressure on the turbine. When the pressure reaches 610 MPa, the residual tensile strength is only 86 MPa, and the strength loss rate is as high as 70%. During the compression process of TiAl alloy, the deformation damage characteristics, which are mainly inter-lamellar cracks and supplemented by trans- lamellar cracks, are formed. Lamellar cracks in the direction of maximum shear stress at 45 ° to the compression axis are the main form of compression damage found in the TiAl alloy. The tensile fracture of TiAl alloy turbine after compression damage occurred at the thin journal near the casting riser side of turbine. The microcracks in the lamellar structure after compression deformation continue to expand under the subsequent tensile stress until the ligament bridge is penetrated, and the small cracks merge into large cracks, resulting in a mixed fracture morphology along the layer and through the layer on the fracture surface.