Abstract: Augmented Reality (AR) is a new research field derived from virtual reality. It is a technology that enables computer-generated information to be superimposed on the real world. Users of an AR system can observe the real scene augmented with computer-generated text, graphics or 3D models of virtual objects. The basic constitution and key technologies of an AR system are discussed. Three types of AR systems proposed for the on-site digital reconstruction of Yuanmingyuan are introduced, including a fixed-position viewing system, a handheld personal digital assistant (PDA) system and a wearable system using a head-mounted display (HMD). Their architectures and working principles are presented. The development status quo and initial experiment results are provided in detail for the fixed-position viewing system.