Abstract: With the development of wind tunnel test techniques, the size of the model is increasing, and the large-field flow visualization is becoming more and more important. Traditional schlieren and other flow visualization techniques are limited by the size of optical elements, and the field of view is difficult to exceed 1.0 meter. On the basis of the focusing schlieren technique, the Fresnel lens are replaced by the tiled LED light sources or other light sources, and the field of view can easily exceed 1.5 meter. After solving the problem of uniform illumination and heat dissipation of light sources, a principle device with 150mm field of view is set up, and the focusing schlieren images of the candle flame and the hot air flow field are clearly obtained. At the same time, multiple focusing lenses can be placed in this type of focusing schlieren system to show larger field of view or different sections. For the large field of view, it is necessary to increase the utilization efficiency of the light sources by the method of, for example, adding convergent lens at the rear end of the light source.