The microstructure and properties of the novel GH4198 alloy under various solution heat treatment regimes were studied using advanced characterization techniques such as electron probe microanalysis, metallographic microscopy, and field emission scanning electron microscope. The results indicated that as the solution temperature increased from 1100 °C to 1150 °C, the primary γ" phase dissolved into the matrix, the grain size increased from ASTM9.5 to 3, and the size of the secondary γ" phase increased. The tensile properties were greatly affected by the solution temperature. It was showed the optimum tensile strength at 850°C was obtained and low temperature tensile strength dropped when the solution temperature increased from 1120°C to 1140 °C. At the sub-solvus temperature of 1120 °C, as the cooling rate increased from 10 °C/min to 450 °C/min, the volume fraction and the size of the primary γ" phase remained unchanged, and the size of the secondary γ" phase decreased, and the microhardness increased. The possible explanations for the improvement of mechanical properties were discussed.