Abstract: This paper aims at studying the transition of boosting to taking-over of scramjet.According to the working requirement of the sidewall compression inlets from completely close to completely open state,a new variable geometry inlet scheme for sidewall compression inlet——variable cowl valve scheme was presented.With the numerical simulation and experiment,the influence of variable cowl on performance of inlets was researched during the process of transition.Based on the numerical simulation,a variable cowl inlet model adjusted by remote control system have been designed,and this scheme has been firstly tested in Mach 3.85 wind tunnel.It proves that,at mach 3.85,the inlet can be opened and closed normally,thus further validating the feasibility of this scheme.