Abstract: Researches on crash compatibility are the current frontier in the vehicle secondary safety field, which is important for the improvement of road safety. The definition of crash compatibility was first identified. Then, the development processes, state-of-the-art methodologies and results for crash compatibility were reviewed. Finally, the latest research direction of crash compatibility was proposed, i.e. combining vehicles' crashworthiness and crash aggressivity into an integrated index to estimate vehicles' safety. Meanwhile, comparison among crash test, crash simulation and data-based methods were presented. The application prospect of crash compatibility was recommended.