Rhopilema esculentum, a large jellyfish, is one of the most economically important traditional fishery products in China. The umbrellas of jellyfish are rich in collagen. Since collagen is temperature-sensitive, it is important to study its thermal stability for the development and utilization of jellyfish resources. In this study, insoluble collagen fibrils (ICFs) and pepsin-solubilized collagen (PSC) were extracted from umbrellas of Rhopilema esculentum, and their thermostability was compared. The results indicated that the amino acid compositions and molecular weights of the ICF and PSC were similar to those of type I collagen, and the differences in the higher-order structure of ICF and PSC led to their different thermal stabilities. Fourier transform infrared spectroscopy (FT-IR) analysis showed that the intensity of the amide I band in the infrared absorption of PSC decreased rapidly, and apparent structural changes occurred when the sample was heated to 36 ℃. When the temperature was raised to 50 ℃, the intensity of the amide I band of ICF changed only slightly, suggesting that thermal stability of ICF is superior to that of PSC. Two-dimensional infrared analysis revealed that 310-helical structures in PSC and β-sheets (low frequency) in ICF were sensitive to temperature changes. In addition to the automatic peak, there were a number of overlapping peaks, revealing that there were some intramolecular and intermolecular interactions among different higher-order structures during the heating process. This study provides a theoretical basis for the development and utilization of jellyfish collagen.