Abstract: Hybrid testing of engineering structures, which combines physical tests and online numerical simulations, can benefit from the advantages of both sides in an economical way. It has been increasingly applied to civil engineering, automotive, aerospace, communications and other engineering fields. This paper reviews the main progress of hybrid testing and its applications in recent years, and sorts out key scientific and application issues. The key scientific issues include the nonlinear stability of time integration algorithms, the control of loading systems, and incomplete boundary conditions. The main application bottleneck is the lack of versatile hybrid test software. Analysis of the current research situation shows that the scientific issues such as efficient and stable numerical integration methods, online model updating technology, and interaction between loading systems and specimen, are worthy of further study; engineering applications in different fields are the determinant factor to promote the development of hybrid testing technology; and strengthening the versatility and fault tolerance of hybrid test software is the key to lower its application threshold.