Abstract: Static compressive test for the studying of compression strength and compression fatigue mechanism of Ni-based Powder Metallurgy (PM) superalloys were conducted and compared to the tensile-tensile strain fatigue.It can be seen that the compressive strength limit of PM is very high,50% higher than the tensile strength limit.The fatigue test with different loading proved that the compression fatigue property of PM was better than the tensile fatigue property,because the compression fatigue failure was very hard to occur.The fatigue mechanism of PM was also investigated using the Scanning Electronic Microscope (SEM).The photos of SEM show that the formation and spreading of the microcrack finally cause the crack.In the compressive fatigue test,the photos show no evidence of crack.