The piezoelectric tuning fork is combined with tungsten probe to form a scanning probe of SPM. The double probe is symmetrically placed at the equatorial circle cross section of the microsphere to form a microsphere sphericity differential measurement system. The dual probes are roughly aligned by a visual guidance system. The microsphere and probes are focused by video microscopy, and multiple groups of photos are taken. Then the aligned images are processed by wavelet analysis edge detection and multi-image fusion, and the image processing results are fed back to the system for accurate alignment. In the actual experiment, the measurement results of the equatorial circle cross section of the microsphere under the alignment method are obtained, and the influence of alignment error on the system measurement results is analyzed.