The effect of heat treatment process on the microstructure and properties of 140 ksi grade In718 alloy was studied. The solid solution temperature adopted three temperatures： 1 023 ℃， 1 030 ℃ and 1 050 ℃， and the aging temperature adopted three temperatures： 760 ℃， 780 ℃ and 800 ℃， the total of 9 sets of experimental data were cross tested. Then the alloy samples after different heat treatment processes were tested for room temperature tensile， -60 ℃ Charpy V-notch impact ， hardness， grain structure and other indicators， and analysis of the fracture structure and precipitates were analyzed. Research has shown that as the solid solution temperature increases， the strength of In718 alloy decreases， the plasticity and toughness increase， the grain size increases and δ phase decreases； At the same solid solution temperature， as the effective temperature increases at any time， the strength of In718 alloy decreases and the plasticity and toughness increase. The aging temperature has no effect on the grain size. γ″phase gradually coarsens from granular and spherical to needle like， and the number of γ″phases also shows a decreasing trend. Among them， the comprehensive performance of alloy is the best after solid solution treatment at 1 023 ℃ and aging treatment at 760 ℃， and the matching of indicators such as tensile strength， yield strength， plasticity， and impact toughness reaches the best level.