Abstract: Chinese olives,Fulan 1and Fulan 2for fresh consumption and Changying for processing purposes,were used in the study to determine the changes on their tannin contents during growth periods.The results showed that the total and soluble tannin in the fruits of Fulan 1and Fulan 2were significantly lower than those of Changying during the fruit development stages.They decreased as the fruits were maturing,but at the same time,the insoluble tannin increased.There was a significant correlation found between the astringency of the olives and their content of soluble,but not insoluble tannin.