Abstract: The microstructure and mechanical properties of FGH 97 powder metallurgy superalloys were investigated using Optical Microscopy and Scan Electrical Microscopy. The mechanical properties of FGH 97 powder metallurgy superalloys with the different porosity level were tested by universal testing machine and instrumented impact tester. The result showed that the yield strength, the tensile strength and the elongation decrease with the increase of the porosities level of the alloy. The impact toughness showed a dramatic decrease with the increase of porosity level of the alloy. The fracture surface shows a large amount of dimples and exhibit micro voids coalescence fracture. Thermal induced porosity promotes crack initiation and the principal crack tends to propagate along the path with high porosity.