Sliding wear behaviour of nanocrystalline Fe88Si12 alloys with different grain sizes has been investigated under low load and speed. The friction coefficient of the Fe88Si12 alloy changes slightly with the grain size, but the wear resistance improves as the grain size decreases. The reduction of the grain size of the Fe88Si12 alloy not only results in the hardness increase, but also is beneficial to form Fe2SiO4 film on the worn surface. The Fe2SiO4 layer can form on the worn surface of the Fe88Si12 alloy even under smaller applied load when the grain size decreases.