The application of artificial neural network for pharmaceutical nondestructive quantitative analysis was investigated. The real data set from near infrared reflectance spectra of trimethoprim powder pharmaceutical were used to built up artificial network to predict unknown samples. The factors affecting network were discussed. A new network evaluation criterion, the degree of approximation, was employed. Owing to good nonlinear multivariate calibration nature of ANN, the predicted result was reliable. [WT5HZ]