Abstract: This paper deals with complexometry to determine the content of tara tannin in tara powder. The results show that:(1)the weight of tara (Caesalpinia spinosa Kuntze)tannin precipitated by zinc acetate (1.000mol/L, 1ml)is 0.1446g;(2)the difference between two parallel determination of complexometry is less than 0.5%and between complexometry and hide powder method 1.0%;(3)complexometry can be used to determine quantitatively the content of tara tannin in tara powder.