A new third-generation nickel-based powder superalloy WZ-A3 was designed through a thermodynamic software. It was prepared by hot isostatic pressing (HIP) + hot extrusion (HEX) + isothermal forging (IF) + heat treatment (HT) processes. The influence of the process conditions on the microstructure of the alloy was studied. The high temperature tensile, creep and fatigue performance of the alloy after supersolvus heat treatment were also explored. The results show that the average grain size of the HIPed alloy is ASTM 8~9, while coarse γ" phase exists on the grain boundary and finer γ" particles presents within grain. After extrusion + forging, the grain size reduces to ASTM 13~14, the γ" particle within the grain is refined, but the number density of large γ" phase increases significantly. After supersolvus heat treatment, the large γ" particles are absent and the average size of the γ" particle is refined to 200nm. Corresponding tensile strength and yield strength of the supersolvus heat-treated alloy at 700℃ are 1360MPa and 1029MPa, respectively, and the elongation and percentage reduction of area after fracture are 23.5% and 17%, respectively. Under the condition of 800℃/330MPa, the time required for the creep strain to reach 0.2% is 229 hours, and the fatigue life at 700°C with a strain of 0~0.8% is 24,500 cycles. The creep and fatigue performance of the alloy are equivalent to typical third-generation nickel-based powder superalloys such as LSHR and ME3. This self-developed alloy has a tensile strength of nearly 50 MPa higher at 700°C and an elongation rate of 3 times compared with the supersolvus heat-treated LSHR alloy, but the yield strength is slightly lower.