The random distribution of gravel makes conglomerate reservoirs highly heterogeneous，which significantly affects the local mechanical response and makes it difficult to control and predict the propagation of fractures caused by hydraulic fracturing. The propagation mechanism of fractures caused by hydraulic fracturing when encountering gravel remains unclear，which makes the design and effective implementation of hydraulic fracturing challenging. In this paper，based on the global cohesion element，a two-dimensional（2D）fracture propagation model with flow-stress-damage multi-field coupling is established on the Abaqus platform. The conglomerate rocks are regarded as a three-phase composite material composed of gravels，matrix，and cemented surfaces on a mesoscopic scale，and the propagation mechanism of fractures caused by hydraulic fracturing when encountering gravel is studied. The results show that fractures caused by hydraulic fracturing penetrate and bypass gravel in conglomerate reservoirs. The permeability and elastic modulus of gravel have different effects on the behavior of fractures encountering gravel. The low permeability of gravel causes the pressure holding，and the fluid pressures at the crack tips increase by 13%；the effective stresses in horizontal and vertical directions decrease by 10.1% and 12.8%，respectively. The high elastic modulus of gravel results in stress shielding，and the effective stresses in the horizontal direction of the area between the tip and the gravel are reduced by 5.8%. The low permeability and high elastic modulus of gravel both cause shear stress concentration on the cemented surface，which increases the possibility of damage to the weak cemented surface and makes fractures bypass gravel.