Abstract: In order to study the influence of coal partical sizes on the effect of hydraulic fracturing during the selection of similar materials, taking the samples with different particle size of pulverized coal forming as fracturing objects, the hydraulic fracturing test was carried out under the condition of the same stress and fracturing fluid displacement with the hydraulic fracturing test system. The results show that the fracture pressure of formed sample is bigger with the increase of pulverized coal size, and the rupture zone is larger and the extended path is more smooth. With the decrease of coal powder size, the expansion of hydraulic fracture is easy to be affected by the coal powder and the expansion path becomes more complex.