In order to solve low sensitivity of flow visualization using a single-pass schlieren system under the conditions of higher Mach number, low static pressure, the double-pass schlieren system with Φ900 mm caliber of light beam of spherical mirror in China, was developed. Compared with a single-pass one, higher sensitivity was obtained, and more flow detail can be provided and the range of application of the schlieren technique can be expanded through a double-pass schlieren system. The out-of-focus flow image was eliminated by replacing colorful knife edge with the LED light source of the four-color-light, by adding the compensating lens, optimizing object lens and adjusting finely the LED light source. The flow image on the common aviation vehicle（CAV） model obtained using double-pass schlieren system was compared with that obtained using single-pass schlieren one. The incident diaphragm was added before the object lens so that a light spot was removed. The vivid flow image on the big blunt model was obtained under experimental condition of Mach number 10, total pressure 2.0 MPa, total temperature 1 100 K, angle of attack from 0° to 15°. The advantage and disadvantage of a double-pass schlieren system was analyzed.