Abstract: Experimental studies on the fine structures of the transient flow and the pressure measurement of the shock train in a constant area isolator with T-control and without controlling method are performed. To study the three dimensional structure of the shock train, the oriented schlieren technique and the nano-tracer planar laser scattering(NPLS) technique are used. The flow visualization results show that these two techniques can obtain the flow structures. Compared with the oriented schlieren, the NPLS technique can catch the fine structures of the flow such as the boundary layer of the turbulence, fine structures of the shock train and the separation area. With the interaction of shock train and vortex induced by the T shaped generator, the shock train edge is bifurcated and closely followed by the second similar structure. High frequency pressure measurements are conducted to reveal the shock train movement and its frequency-domain feature. The shock train location and its movements are detected by conventional statistical methods and the approach of pressure derivative integral. It is revealed that the approach of pressure derivative integral can detect the shock train arriving effectively.