Quantitative characterization of particle morphology of manure is one of the key factors for modeling the fluid flow and degradation mechanism during manure management. This study applied three dispersion pretreatments (water dispersion, oven drying-mechanical vibration and vacuum freeze drying-mechanical vibration) and three analysis methods (scanning electron microscopy, dynamic image analysis and laser particle size analysis) to explore the particle size distribution and microscopic properties of pig manure. Scanning electron micrographs showed that manure particles had an irregular shape; the oven dried mechanically vibrated sample had more aggregates. The comparison between the results of different pretreatments indicated that the vacuum freeze drying-mechanical vibration could be selected as the preferred method because of the soluble components of manure and the aggregates generated during the oven drying process. There were differences in the values of characteristic parameters obtained by three analysis methods, and the dynamic image analysis was suggested as an effective method because of the direct measurement of particle morphology and the high degree of automation. Based on the optimized methods, the median diameter of manure particles was (501±16)μm, the span of particle size distribution was 1.45±0.04, and the shape factors including the aspect ratio and sphericity were 0.57±0.01 and 0.61±0.01, respectively.