Since there was lack of Low-foaming penetrating agents in the market, octyl/decyl polyethylene oxide (OEO) was modified in this paper by silicone-capping to improve its low-foaming property and maintain its excellent penetrating property in the meantime. Three novel penetrating agents were synthesized from OEO and three kinds of methyl chlorosilane reagents and confirmed by FTIR and 1H-NMR. Both foaming volumes and penetrating times against concentrations of penetrating agents were investigated in the concentration ranges used by commercial penetrating agents (0.1 wt.%~0.25 wt.%). Hydrolytic stabilities of these penetrating agents were expressed by means of the variation of foaming ratio against time. The experimental results showed that two of three novel penetrating agents maintained the excellent penetrating property and hydrolytic stability, and all of them displayed much better low-foaming properties than OEO.