Research background， progress and current research status of composites for cryotanks are reviewed systematically. The molding process of composite cryotanks， the safety between composites and cryogenic propellants and the low-temperature mechanical properties of composites are highlighted. Studies have shown that the automatic fiber placement promotes the development of non-lined composite cryotanks. A large number of microcracks are formed in weak areas such as interfaces under cryo-thermal cycling， and the leakage path of low-temperature propellant can be formed under mechanical load. Epoxy resin system with excellent liquid oxygen compatibility， mechanical properties and suitable processing performance is the key to develop composites for liquid oxygen storage tanks. Revealing the effects of cryo-thermal cycling and modification methods on mechanical properties of composites is of great significance to the application of reusable spacecraft composite cryotanks.