polyether modified silicone oil (PESO) was hydrosilylated from hydrogen content silicone（PHMS）and allyl polyether（APE）in the presence of Pt catalyst, the structure of the product was investigated by IR. Polyether modified silicone oil, self-made silicone paste and liquid paraffin as the raw material, together with the compound emulsifier S and other additives, polyether organosilicone defoamer was successively prepared with mechanical emulsification. The results showed that the defoamer was compounded in the conditions of emulsification temperature 70℃ and emulsification time 40min was characterized by better water-solubility, speedy defoaming ability and long-term inhabitation of foam, XP defoaming time is 5s, and the time of foam inhibiting performing is 60min. And the XP defoaming time is about 6s, the time of foam inhibiting performing is about 50min in constant of high temperature of 100℃ and strong alkali of pH 14.