Highly ordered body cubic (Im-3m) mesoporous phenol-formaldehyde resins (OMR) monoliths were successfully synthesized at high temperatures (200-260°C) by the assembly of copolymer surfactant (F127) with preformed resol. The preformed resol was obtained from heating a mixture of phenol and formaldehyde at 70°C. These ordered mesoporous resins synthesized at relatively high temperatures (OMR-200 and OMR-260) show extraordinary thermal and mechanical stabilities, compared with mesoporous polymers synthesized at low temperature (OMR-100 and FDU-15). OMR-200 and OMR-260 samples were characterized with NMR spectroscopy and numerous other techniques. Characterization results suggest that OMR-200 and OMR-260 have much higher cross-linking degree than OMR-100, which might be responsible for the high thermal and mechanical stabilities of OMR-200 and OMR-260 samples. Furthermore, the dielectric constant tests of samples show that OMR-200 and OMR-260 are better than conventional resins, which are reasonably attributed to the presence of porosity in the samples. The unique features of OMR-200 and OMR-260 with superior thermal and mechanical stabilities as well as low-k values might be potentially important for their applications such as heat insulator.