The influence of the δ phase on the toughness of GH4169 alloy was investigated by means of the fracture toughness J0.2BLand instrumented impact experiment. Experimental results indicate that with the increase of solution temperature, δ phase content reduced from 1.54% to 0.045%, and grain size grew up from 12.59 to 35.21 μm. δ phase content has no obvious effect on the strength of the material, but the fracture toughnessJ0.2BL increased from 112 KJ/m to 355 KJ/m, the impact toughness increased from 35 J to 75 J. δ phase is mainly distributed along the grain boundary, there is no strengthening phase precipitation around it. The zone with no strengthening phase near the grain boundary will be formed, it promote the crack propagation along the grain boundary. Moreover, the δ phase itself is the intermetallic compound. Under certain plastic deformation conditions, it is easy to separate from micro plastic zone and form a cavity. In the micro plastic zone, the cavities are rapidly interlinked to form a crack, and the crack grows along the grain boundary with the cavity, which reduces the crack propagation resistance and accelerates the crack propagation. Therefore, the presence of δ phase provides an extended channel for the crack and reduces the toughness of the material.