Hexaphenylcyclotrisilazane (1,2,2,3,4,4-hexaphenyl-1,3,5,2,4,6-triazatrisilinane) is one of the most essential cyclosiloxanes. It has good hydrolysis stability because its phenyl groups have high steric hindrance. It can effectively improve silicone rubber's heat resistance if applied to heat resistance agents to prevent oxidative crosslinking and main chain degradation of silicone rubber side chains. Moreover, when it is heated at a temperature of 400℃ for a long time, it can be formed into a polymer for a good heat-resistant coating.