Medical white vaseline (hereinafter referred to as Vaseline) is an important pharmaceutical excipient. The impurity structure and semi quantitative study of vaseline were carried out using mid infrared (MIR) spectroscopy technology. The experiment found that the infrared absorption mode of vaseline molecular structure mainly includes ν■, ν■, ν■, δ■, δ■, ν■, δ■, ρ■. The infrared absorption mode of impurity structure in vaseline mainly includes ν■, ν■, δ■, ν■, ν■ and the ν■. The impurity structures of vaseline mainly include aryl group chemical compound, carbonyl group chemical compound, amide group chemical compound and water. There is a significant difference in its relative content. MIR spectroscopy has conducted preliminary studies on impurity structures and semi quantitative analysis in vaseline, and has important application research value in the field of medicine. The MIR spectroscopy has preliminarily conducted qualitative research on the structure of vaseline and its impurities, which has important application research value in the field of medicine.