Temperature-induced sol–gel transition of cellulose/silk fibroin/1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was studied from the viscosity and dynamic modulus of the mixtures. The shear thinning behavior of the mixture solution was very obvious with a decrease in temperature. The curves of storage modulus G′ and loss modulus G″ were parallel when the temperature was below 20 °C, indicating that a gel structure exists in the system. The sol–gel transition process was described according to Winter and Chambon’s theory. The gel structure of the mixture system was loosened with the increase of silk fibroin concentration.