The Ni-Fe based superalloy GH984 with microalloying is fabricated by vacuum induction furnace and hot worked by hot forging and rolling. The effect of B and P microalloying on microstructure and mechanical properties of GH984 alloy was investigated by OM, SEM and TEM after standard heat treatment. The experiment results showed that the addition of B and P has no obvious effects on the microstructure of GH984 alloy which has precipitates of sphericalγ', Ti(C, N), blocky MC as well as discrete M₂₃C₆ distributing along grain boundary. Moreover, the addition of B and P has no obvious influence on the tensile strength at room temperature and 700℃. However, tensile ductility increases greatly at 700 ℃ after B and P doping. It is worth to note that B and P microslloying can improve the stress rupture life of the alloy significantly. For example, the rupture life at the condition of 700 ℃ and 350 MPa increases from initial 115.03 h to 984.15 h. Investigation on the microstucture of the creep samples exhibites that B and P could effectively improve the strength of grain boundary and the fractural model from intergranular fracture to intergranular/transgranular mixed fracture.