Cyclotrimethylenetrinitramine (RDX), Cyclotetramethylenetetranitramine (HMX) and Hexanitrohexaazaisowurtzitane (CL-20) own abundant phase transition behavior and characteristics under high pressure/high-temperature and high-pressure. The phase transition routes of three high explosives under different conditions, part of the phase structures under high pressure and p-T phase diagrams were summarized. These researches have provided effective references for the study of detonation behavior and theoretical analysis of energetic materials. Based on current works, there still exist some problems in this area. For example, some divergences still exist about the study of the complex phase transitions, most of the new structures under high pressure are not confirmed and the p-T diagrams are incomplete. In addition, the profound theoretical mechanism of the phase transition has not been sufficiently revealed. Therefore, it will serve as a main tendency to explore the mechanism of transformation between different crystal phases and obtain more information of phase structures in the future research.