To investigate how hydrogen atoms affect the fracture of metallic materials at the microscopic level, this paper develops a model of crack-dislocation interaction incorporating hydrogen infiltration at the crack tip across multiple grains, based on discrete dislocation theory. The model examines how hydrogen alters dislocation distribution on slip planes within grains, affects dislocation penetration through grain boundaries, and initiates wedge cracks at these boundaries. It applies to both body-centered cubic (BCC) and face-centered cubic (FCC) crystals. Through calculations, theimpact of varying hydrogen concentrations and infiltration ranges at the crack tip on dislocation distribution in front of the crack is analyzed. Results show that hydrogen at the crack tip promotes dislocation emission, increases the driving force for dislocation movement on slip planes, and facilitates dislocation penetration through grain boundaries. The relationship between wedge crack initiation at grain boundaries and hydrogen presence at the crack tip is explored. It is found that at large grain boundary angles, an increase in the hydrogen concentration and infiltration range at the crack tip makes it easier for wedge cracks to initiate at grain boundaries. Additionally, the model assesses how hydrogen infiltration at the crack tip influences shear stress in the dislocation-free zone in front of the main crack. It reveals that increased hydrogen concentration and infiltration range at the crack tip enlarge the dislocation-free zone in front of the crack, reducing the shielding effect of dislocations and facilitating crack propagation. This model effectively demonstratesthe influence of hydrogen atoms at crack tips on dislocations in crystals, providing a foundation for studying metal fracture in hydrogen environments.