In this research, a high-precision blue laser focus probe system was developed. The system includes non-contact measurement probe and precision positioning stage. The measurement probe is based on the optical pick-up head of blu-ray player. Because the focus principle of optical-pickup head is astigmatic method, the linear region of the focus range could correspond the position of workpiece and OPU. The precision positioning stage is actuated by the ultrasonic motor and with laser diffraction grating interferometer and the 50x interpolator circuit. The accuracy of blue laser focus probe is 22 nm and the accuracy of precision positioning stage is 60 nm.