The microstructure and hardness of conventionally solidified Ni-xSi (x=21.4, 22, 24, 26) alloys were investigated.The solidification microstructures of different Ni-Si alloys were observed by OM and SEM and the phase composition was indentified under the help of EDX analysis.The macro-and micro-hardness of the Ni-Si alloys at room temperature were also examined.The experimental results indicate that both the microstructure and hardness closely depend on the Si content.Due to the vast formation of primary γ-Ni31Sil2 phase, the hardness of Ni-26.0at%Si alloy was significantly improved compared with that of Ni-21.4at%Si eutectic alloy.However, the fracture toughness was greatly weakened at the same time.The (β31-Ni3Si+γ-Ni31Sil2) lamellar eutectoid structure formed in the primary γ-Ni31Sil2 phase exhibits better ductility than single γ-Ni31Si 12 phase at the cost of relatively small hardness reduction.