The structure and thermal denaturation of cedar pine needle polysaccharides was studied. The mid infrared (MIR) and temperature dependent MIR spectroscopy experiments were conducted. The results showed that the infrared absorption modes of the structure of fried cassia seed mainly include: ν■, ν■ and ν■. In the temperature range of 303 ~ 393 K, with the increase of measurement temperature, the infrared absorption frequency and intensity corresponding to the main functional groups of the structure of cedar pine needle polysaccharides (ν■, ν■ and ν■) have significantly changed, and their thermal denaturation mechanism has been further studied. MIR spectroscopy and variable temperature MIR spectroscopy can effectively conduct research on the structure and thermal denaturation of important natural products ( cedar pine needle polysaccharides).