Abstract: In the potentio-titrimetric determination of more than 3 weak organic polyacids in mixed solutions, the algorithm of principal component analysis (PCA) was applied to the data treatment of titration curves and the algorithm of back-propagation-artificial neural network (BP-ANN) was applied to presumptive calculation of the organic acids. Model showing the relationship between the amount of titrant consumed and the concentration of organic acids in the mixed solution was established. By the proposed method, weak organ polyacids with small relative molecular masses could be determined in mixed solutions without previous separation. The relative deviations between the pridicted values and the actual contents of the organic acids were found to be ≤5.0%.