Cellulose gel membranes have been prepared by a pre-gelation method employing cellulose solutions in aqueous NaOH–thiourea obtained at low temperature. The cellulose gels were then swollen by low-molecular-weight polyethylene glycol (PEG; MW<1000 g mol−1), and the morphology, structure and mechanical properties of the cellulose/PEG gels were studied by various techniques. The gels exhibit high mechanical performance, and the tensile strength of the gel membranes increases sharply with an increase in the molecular weight of PEG from 200 to 800 g mol−1. Moreover, their elongation at break remains stable at 100 %. PEG800 efficiently improves the optical transmittance of the gel membranes at ambient temperature, which is about five times greater than that of a normal cellulose hydrogel membrane. A strong hydrogen-bonding interaction occurs between PEG and cellulose leading to a homogeneous structure, high mechanical strength and good transparency of the gel membranes.