The invention provides a near-to-eye display device capable of automatically adjusting an optical system and a method. The device comprises the optical system, a shooting unit, a processing unit and a motion unit, wherein the shooting unit and the motion unit are respectively electrically connected with the processing unit, the optical system comprises a lens unit and a display unit, the shooting unit comprises a shooting device having fixed focal length and fixed orientation, and the shooting device comprises a left shooting device and a right shooting device. Compared with the prior art, the device employs methods of independent measurement and single-side pupil coordinate position adjustment, so not only can an interpupillary distance of a user be measured, but also displacement of single-side pupils deviating from a center position can be further measured, corresponding side optical systems can be independently adjusted according to measurement results, measurement and adjustment are made to be more accurate, the better display effect is guaranteed, and possible adjustment deviation generated because of simple measurement on the interpupillary distance can be avoided.