Abstract: Rapid assay of crude oil has played a more and more important role in the refineries. The demands and significance
of rapid assay of crude oil are introduced. The advantages and characteristics of mid-infrared and near infrared spectroscopy
methods for rapid assay of crude oil，and their accuracies are compared with that of standard method.

Key words: crude oil assay, near infrared spectra, mid-infrared spectra, Chemometrics