The work aims to realize non-contact inspection for micro defects of spherical surface. Based on laser scattering and shearing interfere, the optical system applicable to micro defects was designed and the precise and adjustable optical system platform suitable for the balls with different diameter was established. The precision accuracy of optical system was determined by the inspection and repeatable experiments of calibration board. The precise and adjustable ball motion platform was built by high precision air bearing spindle. The feasibility of the optical experiment platform to inspect micro defects on ball surface was checked by the inspection experiment for G5 Si3N4 ceramic ball with diameter of 20 mm and the inspection comparison experiment for half-polished bearing steel ball with diameter of 20 mm. For a 4 μm wide and 63 nm high stripe on the calibration board, the signal to noise ration of shearing interfere was 8∶1 which was relatively high. The inspection experiment for 20 mm G5 Si3N4 ceramic ball and the inspection comparison experiment for 20 mm half-polished bearing steel ball were carried out to verify that laser scattering optical path could sensitively inspect the deep micro defects and shearing interfere path could sensitively inspect shallow micro defects. The inspection platform for ball micro defects built based on optical theories can inspect defects of micron level on the ball surface.