This study has been carried out to investigate the precipitation behavior of ${chi}$ phase and effect of ${chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${sigma}$ phase. The ${chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${chi}$ phase into ${sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${chi}$ phase.