Silicone oil with larger molecular weight is insoluble in surfactant solution, while for small molecules, silicone oil is easily solubilized by surfactant molecules, which changes the composition of defoaming agent and weakens the defoaming performance. For the antifoaming agent mixed with silicone oil, it is insoluble in water and mineral oil, so it has strong anti-foaming ability and greatly enhances its anti-foaming effect. Because si-o and si-c bonds are relatively stable, they can be used in systems containing a small amount of acid, base and salt. Most of the silicone defoaming agents commonly used in industrial production are secondary processed products of silicone oil made by adding dispersing auxiliaries to silicone oil, which belong to liquid mixtures. In terms of appearance and fluidity, the mixture can be divided into five types: silicone paste, silicone oil, emulsion, solution and solid.