For ultra-precision Numerical Control (NC) machine tools in advanced manufacturing industry, a high precision measuring method for the taper of a taper gauge was proposed by combining the integral and fractional parts together. The primary principle and the composition of the system were described, and the experimental measurement of a taper gauge was implemented. Moreover, the measurement uncertainty of the system was analyzed. In this method, the high precision indexing system containing a multi-tooth indexing table with an accuracy of 0.10″ was used to ensure the precision and reliability of the integral part, and the laser polarization interference device and a precision rotary table was combined into an angle measuring system to accurately measure the fractional part. Then, the dual-beam white light interference system was used for an accurate positioning. The experiment and analysis results indicate that the measurement uncertainty can be less than 0.3″ when the uncertainty confidence level (k) is 2. The method can realize the high precision taper measurement for any taper gauges.