This study was carried out to investigate the effect of hot forging ratio on the microstructure and mechanical properties of incoloy 825 alloy. Hot forging was carried out at the forging ratio of 0%, 60% and 90% respectively in a range of 900℃~1,140℃ and followed solution treatment was conducted at 1,000℃ for 1 hr. In all the specimens of hot forged of 0%, 60% and 90%, precipitates were not observed. The average grain size of 0% specimen is 82 μm and that of 60% and 90% is 56 μm and 31 μm, respectively. The range of grain size in the 0% specimen is uneven in 182 μm to 31 μm, but the grain size of 90% specimen is uniform. With increasing hot forging ratio, the mechanical properties such as tensile strength, elongation, hardness increased and impact toughness increased by grain refinement. (Received September 1, 2016; Revised September 7, 2016; Accepted September 21, 2016)