Abstract: The microscope imaging and image analysis method was commonly used for the size and geometry measurement of spherical particles. As manual processing for particle images were required, the measurement procedure was time-consuming, and extra uncertainties were introduced. To solve this problem, the automatic particle measurement method based on circle fitting aided recognition algorithm was developed. The automatic particle size and geometry analyses were realized by using circle fitting aided single-particle recognition, followed by the optimization of edge recognition. Comparing with the manual method, the automatic method greatly speeds up the image processing procedure with better repeatability.