Abstract:An experiment was performed to investigate the changes of contents of boron and calcium, and sclereid related enzymes in ‘Huanghua’（Pyrus pyrifolia Nakai cv.）pear fruits treated with foliar application with H3BO3. The results show that the foliar H3BO3 application at different developmental stages could increase the contents of soluble, semi-bound and bound boron in fruits, and at which the young fruit stage shows the best effect, followed by the swelling and ripening stages. In contrast with the application at young fruit stage, treatments at swelling and ripening stages could decrease the calcium content of pear fruits, however, the contents of calcium in cell wall are increased whenever the applications are performed. The contents of sclereid and activities of some enzymes, such as POD, PPO and PAL are decreased under the applications of H3BO3, and the effect of the application at young fruit stage is the best.