As lightweight aggregates are widely used and environment-friendly material that is promising to use in ultra-high performance concrete to reduce self-weight and shrinkage， they have become a hot topic of research at home and abroad in recent years. The design of ultra-high performance concrete is based on the theory of maximum bulk density， and the low strength and porous nature of lightweight aggregates can have a detrimental effect on their performance. The effects of different types of lightweight aggregates and preparation techniques on macroscopic properties are comprehensively discussed and compared， and the mechanisms of lightweight aggregates in ultra-high performance concrete and their enhancement mechanisms are then analysed.