The unsaturated poly(silyl ester) has been prepared by the polycondensation reaction of 1, 3-dichloro-tetramethyldisiloxane with di-tert-butyl fumarate. To investigate the crosslinking reaction of the unsaturated poly(silyl ester), poly(tetramethyl disilyloxyl fumarate) was self-crosslinked and cocrosslinked with styrene in the presence of 2, 2'-azobis(isobutyronitri1e) (AIBN) as a radical initiator. After the crosslinking, the unsaturated poly(silyl ester)s, which were viscous liquids, turned into solid products. The characterization of the poly(silyl ester) and the crosslinked product included infrared (IR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Comparisons were made between the linear poly(silyl ester) and the crosslinked products. It was found that after crosslinking, the important resonance signal for ethenylene (C=C) of the poly(silyl ester) disappeared, which show that the crosslinking reaction is carried out progressively. The glass-transition temperatures of the self-crosslinked and cocrosslinked product were higher than that of the uncrosslinked poly(silyl ester), and the thermal stability of the crosslinked poly(silyl ester)s was better than that of uncrosslinked poly(silyl ester). In degradation tests, the self-crosslinked product degradable completely in 35 minutes and the cocrosslinked product complete mass loss in 5 days and the release of PNA followed the degradation of the crsslinked product. The rate of degradation of the poly(silyl ester) decreased after the crosslinking.