Abstract: It is investigated that the effect of solid-solution cooling methods on the heat-treated microstructure and resultant mechanical properties of a novel Ni-based wrought superalloy with a high content of (~55 wt.%) of γʹ phase. The obtained microstructure after sub-solvus static recrystallization is uniform and fine with 10~30 μm. The solid-solution cooling method has a significant impact on the recrystallized grain boundary and the distribution and size of γʹ precipitates. As the solid-solution cooling rate decreases (water cooling > oil cooling > air cooling), the sizes of primary and secondary γʹ precipitates increase, while the number of tertiary γʹ precipitates decreases. The tensile strengths at room temperature and 850 ℃ are closely related to the distribution of γʹ precipitates, and the smaller the size of secondary γʹ precipitates, the higher the tensile strength. Both the tensile plasticity at 850 ℃ and the stress-rupture property under 850 ℃/350 MPa are largely determined by the recrystallized grain boundary (and the grain size). The quasi-cleavage and plastic mixed fracture can be obtained with the presence of coarsened primary γʹ precipitates and carbides on recrystallized grain boundaries at 850 ℃.