In order to improve the viscoelasticity, gel strength and thermal properties at high temperature of konjac glucomannan (KGM) gels, 0.2,0.5,0.8g, and 1.0g carboxyl cellulose nanocrystalline (CCNC) was used to mix with 1.5g KGM, and the composite hydrogel and blank control were prepared. The microstructure, characteristic functional groups and quality retention of CCNC/KGM hydrogels with different proportions were characterized by rheometer, scanning electron microscope, infrared spectroscopy and thermogravimetry analysis. The results showed that in a certain proportion range(≤0.8g), the viscosity of the system was higher with the increasing of CCNC proportion. Scanning electron microscopy showed that the gel network structure formed by synergistic interaction with KGM was rich in addition of 0.8g CCNC, and the gel weight loss of this compound ratio decreased by nearly 50% compared with that of pure KGM hydrogel at the molten state. The composite hydrogel exerted better thermal performance and retained some gel properties at high temperature. When the mass ratio of CCNC/KGM was about 0.8∶1.5, the viscoelasticity, gel strength and thermal properties at high temperature of the hydrogel were optimal.