disclosed is a silicone - based antifoam composition capable of exhibiting high defoaming activity even at a high temperature with excellent durability so as to be useful in dyeing processes . the composition comprises , as the principal ingredient , a polyoxyalkylene - modified polydimethylsiloxane , of which , different from conventional polyoxyalkylene - modified polydimethylsiloxanes , the polyoxyalkylene groups consist of two different types relative to the molar proportion of the oxyethylene units and oxypropylene units , in addition to a silicone oil compound of a silica filler , a poly copolymer and low - molecular polydimethylsiloxane terminated at each molecular chain end with a dimethyl hydroxy silyl group .