The melt polycondensation of the two kinds of the bis(hydroxydiphenylsilyl)arylene monomers, 1,4-bis(hydroxydiphenylsilyl)benzene and 4,4′-bis(hydroxydiphenylsilyl)biphenyl, was investigated. The thermal properties of the obtained polymers were studied by using a thermogravimetry analysis, a differential scanning calorimetry and a thermomechanical analysis. The IR spectra and the XRD patterns of the polymers indicated that the melt polycondensation occurred in the temperature range from 290 °C to 400 °C. The 5% weight loss temperatures of the polymers synthesized at above 350 °C was around or over 500 °C, so that these polymers exhibited high thermal stability. All the polymers which were obtained by the melt polycondensation of 1,4-bis(hydroxydiphenylsilyl)benzene exhibited the glass transition temperatures. On the contrary, the polymers obtained from 4,4′-bis(hydroxydiphenylsilyl)biphenyl at above 350 °C showed no phase transitions in the DSC measurements. From the analysis of the volatile compounds generated during the melt polycondensation of 4,4′-bis(hydroxydiphenylsilyl)biphenyl by using a gas chromatograph mass spectrometry and the comparison of the 13C CP-MAS NMR spectra of the polymers, it was shown that the cross-linking reaction resulting from the thermal decomposition of the monomers and the produced oligomers took place simultaneously. It was revealed that the melt polycondensation and simultaneous cross-linking reaction were effective to obtain the polysilarylenesiloxanes which have high thermal degradation temperature and high thermomechanical stability.