A technique for the determination of tannin content in traditional Chinese medicine injections (TCMI) was developed based on ultraviolet (UV) spectroscopy. Chemometrics were used to construct a mathematical model of absorption spectrum and tannin reference content of Danshen and Guanxinning injections, and the model was verified and applied. The results showed that the established UV-based spectral partial least squares regression (PLS) tannin content model performed well with a correlation coe±cient (r) of 0.952, root mean square error of calibration (RMSEC) of 0.476 μg/ml, root mean square error of validation (RMSEV) of 1.171 μg/ml, and root mean square error of prediction (RMSEP) of 0.465 μg/ml. Pattern recognition models using linear discriminant analysis (LDA) and k nearest neighbor (k-NN) classifiers based on UV spectrum could successfully classify different types of injections and different manufacturers. The established method to measure tannin content based on UV spectroscopy is simple, rapid and reliable and provides technical support for quality control of tannin in Chinese medicine injections.