In a capacitively coupled discharge with external electrodes, hexamethyldisilazane and octamethylcyclotetrasiloxane were polymerized, and the effects of system pressure, discharge power and plasma gas on the polymerization rate were studied. The polymer structure was researched through IR spectroscopy, X-ray diffraction and solubility measurements, and some properties of the polymer such as thermostability, solvent resistence, hydrophobicity, density and refrection index were also determined.