Abstract: In order to study the influence mechanism of different fracturing fluid displacement and different fracturing times on the effect of hydraulic fracturing in coal reservoir, hydraulic fracturing test device, fracturing pump and similar materials were used to carried out hydraulic fracturing test under the condition of different fracturing fluid displacement and different fracturing times. The experimental results show that: as fracturing fluid displacement is larger, the fracture pressure is larger, the fracture time becomes smaller and the angle between hydraulic fracture and water outlet opening is larger. The fracture morphology is elliptic after first fracturing, then the second hydraulic fracture propagation path is closely related to internal defects and the characteristics of fractured surface.