The movement of solid–liquid two-phase mixtures in pipes is a complex phenomenon with significant implications across various industries, including petroleum, chemical engineering, and environmental engineering. This article presents a comprehensive analysis of theories and methods for calculating the motion of polydispersed solid–liquid two-phase mixtures in pipelines. This study examines classical theories, experimental correlations, and computational methods. Comparing the experimental results with the calculated results shows the local volume concentration distribution of six particles with sizes d1 = 38 μm, d2 = 91 μm, d3 = 128 μm, d4 = 180 μm, d5 = 255 μm, d6 = 739 μm moving in a pipe with an inner diameter of D = 0.11 m at two average concentrations of 0.04 and 0.26, respectively. The comparison results show the suitability of the calculation method.