This paper proposes a new method to improve the three-dimensional (3D) high precision optical surface measurement using a non-contact laser focusing probe. Herein, the displacement or the profile of the tested surface can be obtained by measuring the driving voltage curve to the piezoelectric translator's (PZT) expansion distance. Therefore, we have successfully designed a high-precision auto-focusing 3D measurement system with a linear nano-positioning device. Herein, a dynamic focusing scheme is designed to eliminate environmental disturbances and other noises to achieve a fast and accurate focus. Consequently, the product has considerable commercial appeal and lends itself to a wide range of potential applications. Experiments verify the validity of the proposed auto-focusing method, and the results show that the method's efficiency was higher than that of the traditional calibration method.