The process algorithm of the measurement data of the non-contact grind-fineness-gage measuring device based on the optical spectral confocal technology is studied. The Gauss filtering is used to filter and analyze the whole measurement data, and then the it is carried out in three sections of upper left plane, upper right plane and bottom surface of the chute. The surface roughness and waviness signals of the three measuring surfaces are separated and the roughness value is calculated. The least square method is used for fitting the Gaussian filter median line. The fitting results show the inclination of the straight line on the left and right upper planes in consistent and can be fitted into one straight line. The fitted straight line is used as the datum line, and the depth from the scanning point to the datum line is obtained, and the indicating error of the nominal value of the chute surface depth of 90μm is (0.27~1.97)μm. Compared with the contact measurement of an inductance micrometer, the results show that the data processing method for noncontact measurement is accurate and reliable.