Abstract: A head-mounted display device and an adjustment parameter determining method for the head-mounted display device are provided. The head-mounted display device (100) includes a display screen (101), and further includes a focusing component (102), an optometric component (103) and a control component (104). The focusing component (102) is arranged in front of the display screen (101), and the control component (104) is electrically connected with the optometric component (103). The focusing component (102) is configured to focus incident light during emergence. The optometric component (103) is configured to test a diopter of an eyeball of a user. The control component (104) is configured to determine at least one of a target focal length of the focusing component (102) and a target distance between the display screen (101) and the focusing component (102) according to the diopter.