Abstract: Cellulose nanofibers (CNFs) were prepared by the combined method of acid alkali treatment and mechanical grinding. Polyvinyl alcohol (PVA), CNFs/PVA, PVA and CNFs/PVA modified by polyethylene glycol (PEG) composite hydrogels were prepared by the freezing/thawing method. The microstructure, swelling property, compressive strength and thermal stability of the PVA composite hydrogels were studied. The results show that the microstructure of PVA hydrogels is perfected by CNFs and PEG. After adding PEG, PEG/PVA composite hydrogel has obvious 3D network. When both PEG and CNFs are added into the PVA hydrogel, the obtained CNFs-PEG/PVA hydrogel forms a uniform network structure. The porosity and swelling degree of the CNFs-PEG/PVA hydrogel reach up to (67.5±4.3)% and 980%, respectively. Compared with the pure PVA hydrogel, the compressive strength of CNFs-PEG/PVA hydrogel also increases. The addition of PEG has no effect on the thermal stability of the PVA hydrogel, but the addition of CNFs significantly improves the thermal stability of CNFs-PEG/PVA hydrogel, and the initial thermal decomposition temperature of CNFs-PEG/PVA composite hydrogel increases from 235℃ to 300℃.