Microseismic and acoustic emission (AE) technologies can effectively monitor fracture propagation during hydraulic fracturing in enhanced geothermal reservoirs. To investigate the influence of natural fractures on fracture propagation, the true triaxial hydraulic fracturing physical simulation experiments using granite samples from the Gonghe Basin in Qinghai Province were conducted. Based on AE monitoring data collected during the hydraulic fracturing processes of granite samples with natural fractures and intact granite, combined with injection pressure curves, fracture morphology, scanning electron microscope (SEM) images, and numerical simulation results, the evolution of fractures and AE parameter characteristics in the two types of samples were analyzed. The results indicate that the presence of natural fractures significantly reduces the fracture pressure of the rock. The fracture pressure of granite with natural fractures (17.3 MPa) is approximately 17% lower than that of intact granite (20.8 MPa). The injected water pressure primarily acts along the surfaces of natural fractures, promoting their further propagation. However, under the influence of stress distribution, new branch fractures may still form, mainly concentrate near the direction of the maximum principal stress. Under high horizontal principal stress differences, fractures propagate along the direction of the maximum horizontal principal stress, making it easier to form a single dominant flow channel. Under low horizontal stress differences, fracture propagation is influenced by a more uniform stress distribution, resulting in a radial fracture network, increased overall damage area, and the formation of complex fracture systems. The acoustic emission AF/RA value reflects that hydraulic fractures in granite are predominantly tensile. Acoustic emission response characteristics and changes in the pumping pressure curve exhibit a high degree of consistency, revealing distinct staged evolutionary characteristics. These findings can serve as a reference for field microseismic monitoring during hydraulic fracturing operations.