Grains in the slurry enter into cutting area by steel wire with a certain speed and remove the workpiece material in the free brasive wire sawing. Multi-strands wire is made by metal wires and has many grooves in the surface compared with steel wire. Therefore it can carry more grains into cutting area and improve the slicing efficiency. In this paper, optical glass K9 were cut by multi strands wire (0.25 mm) and steel wire (0.25 mm).The results show that multi strands wire is better than steel wire in slicing efficiency and surface roughness, but the kerf loss is wider than steel wire under the same process conditions.