A composite nucleant with Si powder as the main component was introduced to prepare high-performance multicrystalline (HPM) silicon ingot in this work. The effect of different sizes of Si powder on the ingot performance was investigated and compared with the conventional HPM silicon ingot which seeded from poly-Si particles. It is proved that the composite nucleant with Si powder of large particle size (D50 = 355 μm) can induce small and uniform grains, showing uniform minority carrier lifetime distribution and low dislocation cluster area ratio. Meanwhile, the length of red zone at the ingot bottom is significantly shorter than conventional HPM silicon ingot, which significantly increases the yield of the ingot. The ingot grown with suitable composite nucleant can achieve high cell efficiency and the solar cells have low light-induced degradation (LID) value due to low interstitial oxygen concentration which are comparable to the conventional HPM silicon ingot.