This paper aims to investigate the ambient contrast ratio of transparent displays in AR/MR applications. Transparent OLED displays in indoor environments have been widely applied. However, the high ambient brightness in outdoor environments limits the application field due to poor ambient contrast of OLED. Thanks to the high brightness of the transparent Micro‐LED display, AR/MR applications can be implemented from indoors to outdoors. In this paper, we try to find the appropriate ambient contrast ratio (ACR) range, that is, the viewer sees the appropriate background image and display information simultaneously under different environmental conditions. In addition to using direct transparent display, a switchable black cell is used to extend the adaptive ACR system. Therefore, the proposed ACR control algorithm is demonstrated in a combination of transparent Micro‐LED displays with a switchable black cell to discuss extending the application field from low to high ambient brightness.