Abstract: In order to improve the starting ability of inlet in flight test, reduce the effect of model size and the difference between flight and ground testing, it is necessary to install the forced-transition trip on inlet of air-breathing hypersonic flight vehicles. Through the review and analysis about the design, screening, wind tunnel test and flight test of forced-transition trips at home and abroad, the five main problems are introduced. The five problems are the mechanism of transiton caused by forced-transition trip, install position and geometrical parameters of the trip, influence of the trip on the inlet performance, and the correlation analysis of aerodynamic data between flight and ground prediction for the forced-transition trip. The recommendations are given for the future research directions.