Underground hydrogen storage (UHS) is a promising technique for achieving cost-effective large-scale energy storage. Currently, research and practice related to UHS mainly focus on the storage of hydrogen and hydrogen-methane mixtures in salt caverns and saline aquifers. Shale gas formations are widespread around the world, the stimulated reservoir volume (SRV) with improved porosity and permeability created by hydraulic fracturing could be used for hydrogen storage; meanwhile the surrounding shale could seal the SRV tightly to prevent leakage. This research explores the feasibility of utilizing depleted shale gas reservoirs for pure hydrogen storage and evaluates the effects of operational parameters by combining adsorption experiments and numerical simulations. Isothermal adsorption experiments using methane and hydrogen were performed on shale samples from the Longmaxi Formation. Langmuir equation fitting yielded that the maximum adsorption capacities for methane and hydrogen were 3.81 cm3/g and 1.70 cm3/g, respectively, with corresponding Langmuir pressures of 6.25 MPa and 2.34 MPa. The shale gas reservoir model established with a fractured horizontal well can store 4 × 107 m3 of hydrogen for an extended period. The average recovery factor over 30 injection-withdrawal cycles conducted over 33 years exceeds 0.924. Larger injection-withdrawal rate, longer cycle length and shorter fracture half-length are conducive to hydrogen storage, whereas fracture conductivity has a minor effect. This study serves as a preliminary reference for geological and engineering parameter optimization and economic evaluation of future UHS in shale gas reservoirs.