Accommodation and convergence play critical roles in the natural process of depth perception, and the field of natural three-dimensional (3D) perception in stereo displays has been extensively explored. However, no prototypes of these natural 3D displays are suitable for wear due to the system size and weight. In addition, few of the researches have involved subjects with ametropia. We propose and develop an optical see-through head-mounted display (HMD) capable of diopter adjustment of both the virtual image and the real world scene. The prototype demonstrates a diagonal field of view (FOV) of 42o and an exit pupil diameter of 9 mm, and a diopter adjustment range of -5.5D to 0D. Depth adjustment of virtual image is demonstrated with experiments, the results show the HMD can be further used to investigate the accommodation and convergence cues in depth perception in AR environment, particularly for users with different degree of the ametropia.