The development of a low-cost and efficient solvent for cellulose has been a longstanding challenge in the field of cellulose chemistry. In this paper, we further studied a highly effective cellulose solvent composed of a large amount of dimethyl sulfoxide (DMSO) and a small amount of 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]). The fact that DMSO/[C2mim][CH3COO] can dissolve cellulose more efficiently than pure [C2mim][CH3COO] was fully confirmed with a combination of polarized light microscope and turbidimetric measurements. 1H-NMR spectrographs and conductivity results indicated that an increased concentration of free [CH3COO]− was the main reason for this enhanced dissolution ability. Rheology results revealed that cellulose-DMSO/ionic liquids (ILs) solution had lower zero shear viscosity, structural viscosity index, and viscous flow activation energy, which would contribute to its outstanding spinning property compared to other cellulose solutions. These advantages combined with the low cost of this proposed complex cellulose solvent make it promising to promote its industrial applications.