We report the development of an axon-mimicking phantom composed of hydrophilic hollow microfibres, and evaluate its potential for validating clinical diffusion MRI. Microfibers were fabricated by the co-electrospinning (co-ES) of polycaprolactone (PCL)-polysiloxane-based surfactant (PSi) mixture as shell and polyethylene oxide (PEO) as core, and characterized by scanning electron microscopy (SEM). Three material samples were constructed and included in the phantom within a water bath. SEM images reveal that PCL-PSi fibres in the samples were uniaxially aligned and hollow, with a similar distribution of pore sizes to axons in vivo. MR measurement shows similar anisotropic diffusion behaviour in each sample.