The visual impact of a head-mounted display (HMD) is much more complicated than the traditional display and will influence image quality performance. A psychophysical experiment is carried out to record the subject's threshold to perceive the stray light. Three kinds of virtual reality (VR) HMDs are compared, including Oculus Quest, Vive Focus Plus, and Vive Focus. The results show that Vive Focus Plus has a higher threshold meaning that the observer feels more challenging to detect the stray light. The stray light evaluation can become one of the critical indicators of image quality and apply to VR or augmented reality (AR) content design.