Abstract. Effect of phosphorus on the solidification process of Ni-60wt.%Si alloys was studied in this paper, and the microstructure transformation was investigated by using Electron Probe Micro-analyzer (EPMA, JXA-8840) and Differential Scanning Calorimeter (DSC, NETZSCH 404). It is found that the peritectic reaction in Ni-60wt.%Si alloys would be suppressed by the addition of phosphorus. Another interesting discovery is that the addition of phosphorus can not only suppress the peritectic reaction, but also promote the eutectic reaction (L(l) NiSi(s)+NiSi 2 (s)) in Ni-60wt.%Si alloys.