Using the back-propagation alogrithm and Partial Least-Squares Method the Structure-Activity Relation of Fentanyl derivatives and quantitative analysis of five organic compounds mixtures were studied on the UV Spectrophotometer-PC/AT On-Line system. Results show that the BP Model has good qualitative pattern recognition and quantitative estimation ability, and the PLS algorithm has more accurate quantitative ability and less accurate qualitative pattern recognition ability than BP model.