Gravel sandstone reservoirs are characterized by low porosity, low permeability, and strong heterogeneity, presenting significant challenges for hydraulic fracturing. This study investigates the fracture propagation mechanisms in gravel sandstone formations using a combination of laboratory experiments, numerical simulations, and theoretical modeling. The findings reveal that gravel size, strength, and distribution significantly influence fracture morphology and propagation behavior. Under low stress differences, cracks tend to wind around gravel, while under high stress differences, cracks are more likely to penetrate gravel. Numerical simulations highlight the complex fracture network caused by high gravel content, leading to increased filtration loss, accelerated energy dissipation, and reduced fracture length. A quantitative model was developed to describe trans-gravel behavior, offering theoretical support for optimizing hydraulic fracturing designs in gravel sandstone reservoirs. This work provides valuable insights into the coupling mechanisms between gravel properties, stress conditions, and fracture propagation, contributing to more effective stimulation strategies for complex reservoirs.