Acid value (degree) is one of the important control indicators in the refining process. With the increase of heavy oil, the acidity becomes stronger, and there is an urgent need for a product that can quickly and accurately measure the acid value or acidity of petroleum products. Infrared spectroscopy absorption method is a classic fast analysis method. It is an analytical measurement technology that integrates spectral measurement technology, chemometrics, and computer technologyIt can quickly and quantitatively analyze samples.