This paper reports a new method for dissolving cellulose based on phosphonium ionic liquids (PILs). The method has the potential to produce novel cellulosic and cellulose composite materials in an environmentally friendly way. PILs with melting points less than 100 degrees C and mixtures of dimethylformamide and PILs were used, and are recommended here, due to their negligible vapour pressure, limited reactivity, high thermal stability, and their ability to be easily recycled. The effect of the mass percent of PILs along with the comparison of the effects of different ionic liquids on the viscosity of mixtures are discussed. The limited reactivity of PILs can be used to do chemical reaction on cellulose in the presence of ionic liquids without encountering the problem of incorporation of ionic liquids in the reactions. However, if need be the PILs could also be incorporated into cellulose composites by intramolecular interactions.