The organosilicon high polymers(modified silicone oil) were synthesized by using allyl alcohol polyoxyethylene polyoxypropylene ether (FB), long-chain alkyl esters and hydrogen silicone hydrosilation(PHMS) addition change. And using by infrared spectrum and nuclear magnetic resonancespectrum of its structures have been characterized . A silicone defoamer was prepared with the organosilicon high polymer as active ingredient. It is discussed on the stability , surface tension, defoaming performance of the long -chain alkyl ester segment of its length . The results show that the defoamer performs the most stability, the most uniform particle size distribution and optimal application performance when synthetized with methacrylate tetradecyl methacrylate and allyl alcohol polyether modified silicone oil. The particle size of the defoamer mainly spread in 260 nm. The defoaming time of the defoamer is 6 s, 4 s, 12 s respectively when it is in 5% mass fraction dodecyl sodium solution, 5% detergent solution and black liquor (30% lignin). The defoamer shows better property than RX-504 and 850E coming from .China and Germany.