The unique molecular sieving capability and ultrafast transport of water on graphene-based membranes have been reported in recent years. Although these phenomena have attracted many researchers, the microscopic characterization of the unltrafast transportation of water in the membranes is still absent. Here, we propose to use neutron scattering, which is a powerful tool of probing water dynamics, to study how water moves between the interlayers of the graphene-based membranes.