Abstract: The present disclosure discloses a head mounted display system including a tracking unit, a display unit and a processing unit coupled to the tracking unit and the display unit. The tracking unit is for tracking at least one of a position, an orientation and a pose of the head mounted display system and further generating a tracking result. The display unit is for displaying a virtual scene and a map of the real environment based on the tracking result in a picture-in-picture mode. The present disclosure allows a user to see the virtual scene and the map of the real environment in the picture-in-picture mode synchronously and help the user to understand a current position or a current state of the user in the real environment, which effectively ensures the user's safety and prevents injuries caused by collision when the user experiences the virtual environment.