Atomically thin two-dimensional materials such as graphene and hexagonal boron nitride haverecently been found to exhibit appreciable permeability to thermal protons[1,2],making these materials emerging candidates for separation technologies.These remarkable findings remain unexplainedby density-functional electronic structure calculations,which instead yieldedbarriers that exceed by1.0 eV compared to those found in experiments.Here we studied the quantum nuclear effect in the process of thermal proton going through graphene by recently developed perturbed path integral(PPI)molecular dynamics(MD)on FHI-aims software[3].We find thatthe proton transfer through pristine grapheneis driven by quantum nuclear effects,which substantiallyreduce the transport barrier by up to 1.4 eV compared to the results of classical molecular dynamics.These findings shed light on the graphene permeability to thermal protons.