The gelation of aqueous methylcellulose (MC) solutions containing polyethylene glycol (PEG) occurred in two-steps. First, the gel network was formed by the hydrophobic interaction between MC and PEG at 310-313 K, and then, the gel network was formed between MC chains at 323 K. On the other hand, in the MC hydrogels containing PEG and NaCl, sodium ion assumed to be enclosed by PEG, forming a helix with the hydrophobic groups outward. The sodium ion in the gel was expected to be surrounded by the ether oxygen of PEG as crown ether. The memory of the gel state was kept for 3 days after gelling at room temperature. The period of keeping the memory of the gel state after gelling agreed with the strength of PEG-water interaction. Thermal analysis is effective as a research method for the gelation process of hydrogel which gels by heating and the state analysis of water.