Alloys with a miscibility gap in the liquid state are a broad kind of materials. Many of them have great potential applications in the fields such as chemical industry, automobile, machinery, electronic industry for their special physical and mechanical characteristics. However, these alloys have an essential drawback that the miscibility gap poses problems during solidification. When a homogeneous single phase liquid is cooled into the miscibility gap, it develops into two liquids. Generally, the liquid-liquid decomposition leads to a microstructure with serious phase segregation under the conventional solidification conditions. The application of immiscible alloys is, thus, very limited. In recent decades, many experimental and theoretical researches were carried out to investigate the solidification of immiscible alloys under the normal gravity and microgravity conditions. It has been demonstrated that the rapid solidification technique and sub-rapid solidification technique have great future in the manufacturing of immiscible alloys. Addition of effective inoculants for the nucleation of the minority phase droplets and proper application of external fields, e.g., static magnetic field, electric current pulses, etc. may promote the formation of immiscible alloys with a well dispersed microstructure. Up to date, great progress has been made in this field. The objective of this article is to review the research work in this field during the last few decades.