Abstract: Phase change materials (PCM) have a high potential heat of fusion, and by the phase change at the relevant temperature, a large amount of energy can be stored or released. The phase change materials enjoy the following two advantages: the stability in the temperature control and the absence of moving parts. With the development of space technology, the power of electronic devices increases rapidly. On a spacecraft, the thermal control subsystems are used to keep electronic devices within specified temperature limits, and the phase change materials offer a possibility to store the thermal energy directly as the potential heat of fusion. This paper presents the classification and characteristics of phase change materials. The applications of phase change materials are discussed mainly in the context of spacecraft. Finally, the problems in the study and application of phase change materials are analyzed, the direction for the future development of phase change materials is pointed out.