To prepare a kind of high performance fiber, Single-walled carbon nanotubes (SWNTs) are used as a filler to produce SWNTs/cellulose composite fibers using ionic liquid as solvent. The thermal properties, mechanical properties and structure of the composite fibers are investigated. The WAXD measurements show that SWNTs/cellulose composite fibers are cellulose Ⅱcrystal structure. The results obtained from thermal gravimetric analysis indicate that the addition of low nanotubes amounts leads to an increase in the degrade temperature. The tensile mechanical properties show that initial modulus and tensile strength considerably increase in the presence of nanotubes with a maximum for 77.8% and 27.2%.