Abstract: With the increase of capsule requirement, a method for batch characterization of the diameter and sphericity of poly (-methyl styrene) (PAMS) mandrels is developed based on the VMR microscope system. The sources of uncertainty in characterizing the diameter are analyzed and every uncertainty component is evaluated. The 95% results of a 1 mm standard ball are in the range of (998.2-1.2) m to (998.2+1.2) m, showing excellent precision and stability of batch characterization. The characterization method is also used in measuring the PAMS mandrels. Compared with the results characterized on MM-400 microscope by hand, the deviation of the diameters of PAMS shells characterized by batch shows unidirectionality, and the maximum value is about 10 m, within the requirement of 15 m.