As the aperture of wire drawing die is becoming smaller and smaller,the parameter measurement of the common wire drawing die inner hole can’t meet the requirement. The high precision measurement of micro aperture pass was realized by combining the rotation measurement and laser diffraction. In the measurement process,center shaft of drawing die was continuously rotated by controlling of stepper motor,which produced different diffraction effects. The diffraction images with round or elliptical hole were sampled respectively on the CCD. The pass parameters of drawing die were measured through the function relationship between diffraction images and pass parameters. Finally,the measurement error of about 1% was obtained. The results show that the system has good reliability and high precision.