Abstract: The on-line measurement and rapid analysis of the internal volatile and external volatile ingredients of propellants are very important to the quality of the products. It’s a key technology in the realization of flexibility in the processing of propellants. A fast method was presented on the ingredients of the product on the flexible-production line with NIR diffuse reflectance spectral analysis. The spectra of the samples were collected, the calibration model with a simplified PLS algorithm was established, and the ingredients of products were predicted with this model. This method can be used to measure ingredients of products rapidly, accurately and in real-time without the need of pretreatment for the products.