Abstract: Many studies about boundary layer transition had been carried out in the last fifteen years with the quick development of hypersonic technique. Much information about Tollmein-Schlichting wave, crossflow instability and Görtler instability had been obtained. Some transition criteria, transition models and e^N method had been developed and can been used to predict hypersonic transition problem in engineering. At the same time, the test capacity of wind tunnel had a large improvement by developing new measurement techniques and building hypersonic quiet tunnels and large nozzle convention tunnels. It is expected that the investigation on boundary layer transition follows the tendency of hypersonic vehicle closely, so great attentions need to be paid on elliptical cone and flared cone. It is promising that the interactions are studied by using PSE and DNS between Mack mode, crossflow instability, Görtler instability, and flow separation. In order to predict transition with high precision, the methods of e^N based PSE, special transition criteria, and transition model is consideration of physical insight are the keys. Furthermore, test capacity need to be developed, such as the increasing Reynolds number and nozzle size for quiet tunnels, the noise level reduction of convention tunnels, and the measure method development by combining point and surface techniques and flow visualization technique with high fidelity.