Aiming at the problems of inaccurate measurement of human eye parameters and inconvenient operation brought by the semi-automation of refractometers, a fully automatic refractometer is designed by means of optics, mechanics, electronics and computing. An automatic positioning method for human eyes is proposed. The short-focus camera is used to realize the alignment between the eye and the camera plane, and the pupil camera is used to realize the focus of the longitudinal distance between the eye and the camera. The optimized template matching algorithm is used to locate the human eye area in the short-focus camera image. The pupil contour ellipse is fitted according to the pupil characteristics. Then, the offset between the center of the ellipse and the center of the camera in the plane X/Z direction is calculated, and the 3D moving platform is controlled to move to the center of the human eye. In distance focusing, the Hu invariant moment method is proposed to extract the middle line of the reflection target ring in the pupil camera image, and the ellipse is fitted to calculate the ellipse diameter. A method of calculating the longitudinal distance (Y direction) between the human eye and the camera by using the ratio of ellipse diameter-reflected light spot distance is proposed, and the 3D moving platform is controlled near or far from the human eye to achieve focusing location. The experimental results show that the accuracy rate of human eye positioning is as high as 98%, and no significant difference is found in positioning speed compared with the market prototype, making it suitable for practical application.