Amorphous tin oxide (a-SnOx) nanohelix (NH) structures as an anode for Na-ion batteries are fabricated on copper foil by oblique angle deposition method using electron beam evaporation without any additives. With freely controlling the degree of crystallinity, three-dimensional NH structures have high porosity, high aspect ratio and large surface area to result in remarkable reversible specific capacity and stability for volume expansion. The reaction mechanism issues as well as more fundamental advantages of a-SnOx NH structures as an anode for efficient Na-ion batteries will be discussed in detail.