Microstructure and high temperature tensile properties of five powder metallurgy FGH98 alloys with different Ta content were systematically investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM) and high temperature tensile testing machine. The results show that: Ta can obviously eliminate the prior particle boundaries (PPB) and change the morphology of secondary γ'-phase. Ta can promote the generation of tertiary γ'-phase. Ta improved the high temperature tensile strength and yield strength of the alloys. When the Ta content was 2.4% (the same below), the alloy has the preferable plasticity. Alloys without Ta and with 1.2%Ta showed a crystalline-like fracture surface while the alloy with 2.4%Ta showed ductile fracture surface. Alloys with 3.6%Ta and 4.8%Ta exhibited transgranular and intergranular cleavage fractures. The alloy without Ta deformed mainly by generating a large number of twins and dislocations bypassing the γ'-phase. With the increasing Ta content, the dislocations shear the γ'-phase, therewith produce a large number of stacking faults.