The Background Oriented Schlieren(BOS) technique can provide a wide and quantitative measurement of the flow density field. However, as the technique is vulnerable to vibration, the technique’s accuracy is often affected by environments and test facilities. A vibration tracking marker was introduced to compensate for the vibration error. The background image movement outside the flow region was also tracked to check and correct the vibration of the background image itself. The nozzle flow of a supersonic blowdown wind tunnel was then diagnosed using the improved BOS technique. The result showed that improvement is capable of correcting vibrational errors. However, the technique was still vulnerable to rotational errors. This study complemented the vibration correction method, which is one of the main causes of error in the BOS technique.